It cuts both ways. Visa/MC have to deal with high numbers of fraud on these sites. Even worse, they have to deal with “fraud” where husbands get caught and blame it on fraud. It seems like linking porn accounts to phone numbers is the most sensible solution but how popular is that idea going to be?
But shouldn't that be handled on a commercial level? Riskier site, with higher chargebacks or less identity verification (like the historical no-signature-present) get charged higher rates and fees. This already happens, but the rates could be even higher if needed. There doesn't seem to be any need to police content, that is just factored in the risk and thus cost of service.
How about we stop trying to by default create identifier networks with the sole purpose of increasing the amount of information open to disclosure via Third Party Doctrine? The closer you get to a de facto UUID for a person, the faster it's going to be abused.