That should be a myth by now. Would be interesting if e.g. Stripe could share the fraud statistics for onlyfans. The banks probably do this purely to keep up appearances and avoid potential bad PR.
Congress, for one. There's a history of bills that are meant to target trafficking scooping up consensual practices as well (see also the Mann Act, SESTA/FOSTA). I'm not sure how influential the threat of something like this was here, but it can't help:
https://www.huffpost.com/entry/human-trafficking-banking-bil...
"Ah shit, honey. Somebody must have stolen my card."