If porn sites start taking bitcoin, then we will wait for a transaction for about a week. Bitcoin is not the best way for mass use.
I think there is nothing wrong with porn sites using Bitcoin, if you have problems with transactions I do not think that is a good reason to wait for the transaction to be a week, because it all depends how the transaction goes.
I think one of the reasons why porn sites aren't accepting bitcoins at all or any other cryptocurrency is because it's totally anonymous. They don't have a way to confirm that you are actually 18+ years old and you're in a legal age to watch porn. They are just trying to protect themselves from future problems that might occur if they have accidentally given premium accounts to people that aren't in the legal age. Of course there are sites where you can watch freely but there are certain agreements in the website that you are watching because you are 18+ and you confirm so.
Even if they try to partner the bitcoin payment with some ID verification, it still wouldn't work as good as when they use a CC to verify your details. Everyone has got a fake ID but not everyone has a live CC that aren't theirs. What I'm trying to say is that it's harder to do identity theft if there's a CC required. But it's also possible that crypto payment just isn't requested enough for them to upgrade their system into accepting it. There's a lot of unsorted laws about cryptocurrency right now. There are places that doesn't have any law about it while there are places that banned crypto. I guess the jurisdiction where the porn sites are located either have an unclear statement about crypto or have it banned. These are all just speculations. I might be right but I can also be totally wrong.