Looking over my personal usage stats and my clan's usage stats; and contrasting with the community usage stats, I noticed something interesting. One of the least-used archetypes, and one rife with frames with bad or polarising reputations, is the hybrid damage buffer/CC frame. Meanwhile these are really popular in my Alliance, as we have a few stalwarts spreading the good word. (I'm doing my part for Banshee propaganda.)
I can say that the usage stats reflect a sentiment I hear a lot: "just use ". In this case, Nekros and Octavia dominate this particular role at 3.2% usage apiece, reflecting community belief that Octavia is the best frame in the game and renders other CCs useless. Meanwhile there is a harsh dropoff in the buffer/CC archetype after Octavia (or Nezha if you count him). The next most used is Mag at 1.5%, then Frost and Zephyr at 1.1%. After this, the rest of the archetype all have less than 1% usage.
Other support archetypes are in a similar place: the healer/buffer is dominated by Wisp, and the damage/CC archetype by Khora.
A second factor is the "death spiral". If a frame has a bad launch or a rough patch as the meta shifts around them, they seem to never shake that bad reputation. For example, year on year, even with extensive positive coverage, Zephyr sees very little change in equip time. Yareli is Turbomurder Water Nezha now, but it's still a common sentiment that she's squishy and has poor damage potential. Everyone has an opinion about Sevagoth even though nobody plays him.
A third factor, and I think another kind of death spiral, is unappealing meta builds. For example, Nyx is dominated by Assimilate builds, Banshee by glass cannon builds, Caliban's meta being a complete mess, one-button Frost and Loki builds, and so on. People don't invest into the frame because it has been typecast and the builds ossify, and if the builds aren't fun to play, nobody invests or experiments, and the cycle repeats.
So, that's my take. I'd love to hear your opinions!
What makes supports unpopular? Many reasons. For one, we have a lot of warframes that are completely self reliant and can do any mission in the game alone, either with their abilities or good guns. Supports also tend to not stack with themselves that well. A Wisp and Mesa are gonna work great together, but Wisp and Trinity? Not so much. Meanwhile having multiple Mesas is nowhere near as bad, you will just have less things to shoot. Supports also rely on your teammates to have a brain to actually use your buffs properly, and we all know how the average public player is. The biggest reason of all is that Warframe rewards speed, as most content is incredibly easy but highly repetitive. Cracking open relics as an example, all that matters is how fast you can kill and how quickly you can extract, so appropriately people will bring nuke frames to speed things along. Death is also by far the best CC effect, all enemies are vulnerable to it and a dead enemy does nothing to threaten you or impact the mission (they also drop loot). Why CC enemies when I can cast 4 as Volt and watch the numbers pop? All of that together makes support/CC frames an unpopular pick, they are still good, sometimes straight up better than other common picks, but the common picks are lower effort while still getting the job done, and for most players that's all that matters.
With the first point, I want to clarify, most "supports" (by my understanding of the term) actually have some kind of debuff that increases their damage. For example Nyx has access to Pacifying Bolts which is functionally a one-handed Tharros Strike, even on SP spawn densities. Enemies with no armour are functionally at a 20x or higher damage multiplier, albeit less assuming you're running a Corrosive weapon and not building Viral around fullstrip. Frost has access to fullstrip and then some combination of a personal CC/CD buff, or a party-wide Viral amp through Freeze Force. Banshee has Sonic Fracture and optionally Sonar for the funnies or on Demos, Eximus and Acolytes.
The kind of support frame I was focusing on has good personal damage tools, but the support comes from the fact that these tools benefit the whole party as well.
Trinity is a bit of an outlier in that she's all in on survivability, especially with something like Vampire Leech/Nourish builds which have the potential to shieldgate everyone constantly. Admittedly I think she and Wisp are what people think of a "support" as, and not say debuffers like Frost, Caliban, Sevagoth etc.
Edit:
That said, this is a great answer. It's very insightful as to where my own personal biases were formed: the kind of content I do, which is primarily long solo runs, 5+ rotations of endless and Duviri, and usually with Alliance members and friends. In these situations, debuffer CCs shine. I do think someone like Nyx is very misunderstood for linear speed missions with pubbies though, as Pacifying Bolts is a very powerful damage booster when you're moving quickly.
The problem is that all of that is completely unnecessary in 99% of the game people actually play (we're not talking about Steel Path endurance). Armor stripping especially is a null point as Pillage is an incredible subsume that is used on a lot of nuke frames that struggle with high enemy armor. Is Banshee's Sonar a huge dmg buff? Sure. But I can bring my Revenant with 105% Roar subsumed and any good weapon to a Steel Path Circulus on Lua, stay to rotation C and not have any issues killing enemies while not having to worry about a thing because of Mesmer Skin. Mesa can full armor strip in two casts of Pillage while having 95% DR, constant shield gating and an auto aim weapons for low effort crowd annihilation. Also, why would I bother supporting my teammates if I can instead get the job done myself? Why would they bother supporting me if they themselves can bring a frame that can get the job done themselves?