There is also the expectations of your "fans". On Insta or Tik Toc or what have you, they turn their follower count into ad dollars or perhaps other modeling gigs or the odd appearance fee at a club. But they are removed from their followers a bit. If I follow some Insta model, I'm actually shocked if she responds to a DM. If I'm subbed to an OnlyFans, now I have an expectation that a DM will eventually get a response. And the more I'm paying the quicker I expect it. This means one of two things, either they have to get an agency to handle all that for them and hope they do a good job at pretending to be them and they aren't discovered and face a ton of blowback, or they dedicate quite a bit of their time to managing their page. A lot of money in it for the ones that are successful, but really, it is a full time job.
And with an OnlyFans you also have to worry a lot more about people crossing boundaries with you. With the one on one flirty nature of a lot of these interactions , it's not uncommon for a sub to forget that it's transactional and not an actual relationship. OnlyFans comes with a lot of headaches that just isn't worth it for many women. and all that is outside of the whole stigma thing, which as you note is its own ball of yarn.