Just as gambling, then the presence of bitcoin will make more porn sites. the main reason bitcoin is the anonymous user, a porn site surely did not want to if his identity is known so that they will choose a bitcoin.
Not only that because of using bitcoin those transactions would really speed up compared on the tradition ways before and as you said the anonymity is there regarding when someone plans to purchase premium he wont expose himself already to the site which is really great for those porno lovers out there.
Guys... (assuming this isn't a girl's toppic, except from the work opportunity aspects) all these pron producers have to comply with age verification checks. To protect the teenagers from knowledge about things, until stumbling into them on their first date. It's a big conspiracy run by the adults. And it's done right, there is no fun for them kids knowing in advance. Let them find out on their own. Explore. Have fun.
But!
That means in contrary that anonymity isn't needed for pron payment channels, at all. If you have to register with passport, the payment channel no more matters afterwards.
Did you never considered?