> Way to split hairs. Something being against the ToS can still be legal.

Well, no, violating a binding legal agreement is illegal.

> Prostitution obviously cannot physically happen on an online platform, but it sure is a convenient way to advertise and attract customers, and serve as the payment processor.

Which is explicilty prohibited by the law in many places OF operates, and judging from the number of people who are creators on the platform I've seen complaining about people jeopardizing their status with the platform by soliciting it on the platform, also by the actively-enforced terms of the platform. OF is simply not “legal prostitution”, and it is ridiculous to describe it that way