I personally think it's because a lot of people, to a degree, are still stuck in binary thinking.

Sure, they might acknowledge that gender is a spectrum, and people can identify anywhere on that spectrum, but they can often still perceive the underlying traits often associated to that gender as inherently tied to it.

So while someone might accept that trans girls exist, and are, in fact, girls, they might also carry with them the assumption that wanting your gender to be that of a girl means you also naturally want your body to replicate the stereotypical form of one.

It's sort of like a secondary wall that they have to break down. The first was regarding how gender itself is tied to identity, not solely to biological characteristics, but they've yet to break down the second of assuming that because you identify as something, you also want everything stereotypically considered to be a part of it.

I'm no expert, nor am I trans myself, so take this with a large grain of salt, but considering years ago, I once had similar inclinations before getting closer with various trans people I now know personally, this is the best explanation I can come up with.

I had SRS, and it was great for me, but it's obviously a very personal thing. And it's certainly not cheap, easy, or without the risk of complications. People latch onto it because many people just fundamentally believe that genitals=sex=gender. And genital configuration is the traditional definition of "sex." Some contexts still work this way. In most of the US, prisons operate based on genitalia, not personal identity, secondary sex characteristics, or legal sex. In most of the US, if you were to end up in jail, you would be sent to a men's prison.

It's just a deeply, deeply rooted cultural thing. Genetics and chromosomes weren't even discovered until the mid 20th century, and even chromosomes aren't really all there is to a person's sex. But for centuries prior, your sex was simply your genitals, your gender was your sex, and you genitals were unchangeable. That centuries of cultural inertia is what is being resisted when someone with typically-male genitalia adopts a female gender. Even if you are on HRT and gain female secondary sex characteristics, you still have the primary sex characteristics that were traditionally one-and-the-same with the male gender. It obviously isn't that simple, but for centuries of western history, it was.

Among some, both cis and trans, there's also a sense of needing to prove that a person "really is" trans. Most of the effects of hormones are reversible. Genital surgery isn't. Some people will always be more comfortable accepting someone's gender identity if they "really commit to it." And permanently turning a penis into a vulva is a pretty obvious sign of commitment. Some women just invariably see "penis=threat," and some men see "penis=competitor." There's a lot of cis women who would be more comfortable accepting and treating a trans woman as valid if they know she couldn't force herself on them even if she wanted to. (At least in terms of penetration.)

I know this isn't how things should be. I don't think you need to have bottom surgery to valid in your gender. But genital configuration is something that is burned into the very core of the psyche of how most people interact with each other. It's a fundamental component of standard cis-hetero gender relations. And it's just always going to be a much greater reach for a lot of people to accept a trans person as valid with their original equipment than without their original equipment.

Hell, gender is assigned at birth almost 100% based on genitalia. You were (I assume) assigned male at birth, and unless you were born with ambiguous genitalia, it's extremely unlikely anyone ever tested your karyotype. And for 99% of cis people out there, they've simply stuck with the gender they were assigned at birth, have put zero thought into it, and were simply assigned that gender based on their genitals. The vast majority don't even know their own karyotype; they just assume it. For most people, their gender, their sex, and their genitalia are all indistinguishable. And it's really hard for a lot of people to get past that.

Well, I'm not able to posit an answer to this as to why trans people don't consider it valid, but I've seen discussions about it.

What I can point to is the cis side of things. Ignoring the jerks that are coming from bigotry, berated that's the answer for them: bigotry.

But I know some people that are supporters of trans rights, but still hold onto that view, that until someone, particularly mtf people, has bottom surgery, they haven't transitioned, or at least not fully.

Now, it took me a bit to wrap my head around it, why someone that would want to transition at all wouldn't want all possible methods used. And it comes down to the binary. People in general still haven't grasped that not everyone is binary in the first place, much less that transition is not necessarily about changing the body.

It's certainly a big thing, it's important, but making that mental leap from "oh, they want their body to be right, and that means being as direct a match to the organs and body shapes of the confirmed gender as possible" to "oh, everyone can have different needs regarding any given part of their body to be transitioned for themselves"

See, a lot of the fight about trans rights revolves around genitals. A lot of what people that are binary build their idea of gender around as they learn and age is the sexual characteristics, with the primary characteristics of genitals being the most defining. In other words, me being a cis man, my gender identity is very much tied to my genitals as the most relevant factor in my body matching my inner self. I've moved past it being the only factor (though that took time), but my junk is part and parcel of the physical aspects that make my body a man's body (for my body, not others')

When the tie between gender and sex and identity are first developed, it's inside the self. So the closer one hews to the binary, the more import ends up being placed on genitals because of being at the binary points. "I am a boy/man, and I have a penis, therefore men have a penis". We all start with our own viewpoint.

And, for some trans people, genitals are a primary factor. But they don't have to be, and it takes a combination of exposure to the possibilities as well as willingness to change one's mind to truly grasp that.

You know the most significant thing that helped me get that transition confirmation isn't purely about surgery? It was talking to trans men. The bottom surgery options aren't as sought after among the trans men I've known. Hormonal effects have turned out to be perfect for them. It confused me at first, what with my gender identity being significantly tied to my genitals looking and working in a distinctly cis way. But it eventually broke through that you don't need a cis penis or testicles to be a man.

And that is what directly led to internalizing that the notion surgery for trans women isn't necessary either. If I lose my penis, I don't become a woman. Recognizing that fact flipped my head. It means that, just like phalloplasty not being necessary to become a man; you don't have to have vaginoplasty to be a woman.

A woman that happens to have a penis is still a woman.

But it takes knowing enough trans people, having enough conversations about it, to break out of the binary way of thinking even for trans people that are binary.

To refocus, I think that the reason people think you have to have bottom surgery is that they've not had the right combination of events to make them break out of binary thinking as the default. Now, the ones that refuse to accept the fact of it not being the defining characteristic, that's as much about humans being stubborn and sometimes arrogant about our own thoughts and opinions being the right ones. Most of us don't want to change our minds at all, about anything.

But I suspect that, given enough time and exposure to the concepts, anyone that's otherwise on the path of understanding trans people will get there eventually. It's only the ones that aren't trying to understand that won't get there.

My theory is that most people don't think about who they want to be, just who they are, and for many people that revolves around their genitals. If they think they're who they are because of their genitals, then, logically, to change who they are, they would have to change their genitals. Then, because most people don't think about how their experiences aren't universal, they apply that to others.

I don't think you'll find a satisfying answer to that question.

Trans-medicalists tend to over rationalize the subjective trans experience and many of them are incapable of separating their own, personal desires from what ought to be for everyone. It's very human to choose a path for yourself and justify it by assuming it's the only "right" way, trans people, while generally much more self-aware than other population groups are not immune to normal human foibles. In fact, dysphoria and other mental health issues related to transness can amplify disordered thinking and lead to outcomes like gatekeeping transness behind expensive, often unattainable, medical interventions.

It's not so much that they are unable to understand, but are unwilling because facing a truth that medical intervention is not a required part of the trans experience can create serious cognitive dissonance, especially if the individual has taken steps on their medical transition they felt compelled to but would not have chosen otherwise.

Folks like that are frustrating and damage the overall efforts of the community to find acceptance. Still I wouldn't hold it against them, we're all only human and doing the best we can with what we have.

Also VERY important, a non-trivial portion of trans-medicalists are either suffering from internalized transphobia or engaging in discussion cynically (such as trolling, or intentionally spreading disinformation).

I identify as trans, and I don't want to/have bottom surgery (I'm afraid of any kind of permanent body modification). I also don't really look fem, but that doesn't stop me from calling myself trans. it just feels right.

Joke's on you. I was born a bottom.

Because for many of us it's lifesaving. I still really want it but I want it less than I did before since HRT has shrunk my penis substantially, before I literally wanted to cut my penis off and I fantasized a lot about doing it. I had friends who actually did, and they still ended up killing themselves bc of it. Bottom surgery saves lives.