I don't know if you were aware but PornHub had a massive scandal with the content people were uploading that led to them basically deleting the majority of user contributions altogether. So maybe not so easy for them either.

Wasn't that a copyright issue? People uploading stuff for which they didn't own the authorship rights?

OnlyFans does not seem to have that problem at any significant scale at all, so why can't they figure out a way to handle payments for porn?

No, it was primarily about various forms of nonconsensual and underage content.

pornhub is having this issue exactly. They got PNG'd by all the payment processors. They only have crypto payment options now. My bet is pornhub is doing a lot worse now than they were before.

https://bravenewcoin.com/insights/pornhub-crypto-news

Their FAQ is still showing that they offer credit card payments via Probiller, but clicking onwards does indeed show them temporarily not accepting credit card payments, defaulting to a SEPA transfer instead.

i imagine their income from a few years ago is much larger than it is today.