Are you asking how they're different, as in what makes the different hairs come out the way they do?

Or, is it wondering what the point in the difference is?

The first one is pretty easy. Follicles. The follicles determine how hair is shaped, how it feels, and how thick it is. The way they chain the materials together determines how straight/curly it is, how coarse/smooth it is, the diameter, and how long it grows before falling out and getting replaced. You can look at cosmetology faqs for the details. There's some debate on some of the details, but that's the gist of it.

As for why there's a difference in anything but length, that's harder. Evolution is the broad answer. At some point, the genes that made our hair the ways it can be were advantageous enough to end up fairly universal for all humans.

There are no certain answers, and I don't think it's possible to have many when it comes to that side of things. But, the two big ideas I've read about or heard about are friction vs scent and display vs temperature.

When it comes to pubes, there are people that have the hypothesis that they're pheromonal concentration and dispersion assistance. There's also the idea that they prevent friction leading to skin injury over time, and/or during sex.

Between those two, I kinda doubt the first. Humans just don't have much in the way of pheromones, and we suck at detecting them. Seems pretty strange to need the coarse and curly hair down there when the associated senses aren't there. The second makes sense on the surface for sure; just shave your junk and put on some stiff pants and you can tell the difference with and without pubes in five minutes. And there is a degree of increased skin irritation without hair, but I don't see that as being as big a factor. I personally suspect air flow has a factor in there, but I have nothing to back that up with other than genitals being very temperature responsive and humidity needing. But I admit it could be both or neither, I sure don't have the expertise to say (and there aren't many people that do)

Head hair, you get the usual debate on it growing the way it does for environmental protection against heat and cold, usually versus the possibility of it being for display. I say it's both because it's pretty unusual to find any critters with a major trait like that not having multiple functions.

Anyway, years ago, I asked the same question and went digging. I didn't give enough of a fuck to write things down, but that's the basics I picked up.

They’re growing from different types of hair follicles. Why do we have different types? I don’t think anyone knows for certain. Possibly something to do with the development from the full body hair of our ancestors to the partial coverage we have today.

Not all human races share this trait. I saw a documentary about aging Chinese males and hairloss (don't know their race but the procedures were in china and they had genetically Asian traits), and a lot of them could use pubic hair from their own body to substitute, as it is much closer to their head hair when comparing hair characteristics. Very cool.

This post is made semi-jokingly, but it's still a real question of mine btw. In other words: why is ball hair all fucked up when head hair is so smooth?

I for one am happy I don't grow a long, smooth mane between my legs. Still not happy with pubic hair, though.

If I had to guess it would be thicker and curlier because it supposedly has to do this job of spreading pheromones and not get too much in the way of action. Also, you get more friction from moving your body in those places, so hair too thin might not cut it, and break off. Or something.

I really want to get laser hair removal, btw. Evolution has been leading up to lasers, everyone knows that.

Also, hair stylists really should be more specific. You said you style hair, suddenly there's a difference!?

Well now I can't stop imagining what life would be like if my pubes, beard and mustache were as soft and long as my head hair. 🤔

I think I'd be an afghan. Like the dog, not the ethnicity.

My head hair falls off. It sure is different, just not in a good way. :)

Fact 1 - sexually active people subconsciously look at peoples' crotches when meeting them.

Fact 2 - evolution doesn't fine tune things if they're good enough to get the job done well.

So the fact that pubic hairs are unsightly crazy-looking things might not be because they are fine tuned to be like that - it might just be because they do their job well enough and they just ended up looking like that.

What job could that be?

To confirm visually that you are sexually mature.

That may literally be it - a localised fuzzy indicator of whether or not you're able to make babies.

Pubic hair is much, much thicker.