You say this like porn viewers don't have a huge incentive to make sure PORNHUB CO. doesn't appear on their bank statement or that some shadow profile isn't tracking their viewing habits. Hell, private browsing was practically invented for porn and [insert non-porn plausible deniability excuse].
I think the porn industry is in a unique position where if their stance was that highly regulated, completely image based, ads served securely through their domain was the means by which the site was funded while maintaining the viewer's anonymity they could find themselves on a lot of default white-lists.
Do they? I mean, honestly, who isn't a porn viewer? Who on earth would you, personally, think it to be scandalous to have a porn subscription discovered on their credit card? Anybody? What is the incentive?
I thought OP's porn example was pretty good. The entire world crushes porn (even when it's taboo or illegal), and yet still refuses to pay for it.
Believe it or not, there are people who never watch porn. The industry's sleaziness turns some people off, and some people just aren't into it.
http://www.independent.co.uk/news/uk/politics/smith-ordered-... : mostly this was about putting the cable TV bill on expenses, but all the papers were particularly outraged at finding PPV porn on the bill.
Not even porn can get many people to prefer a subscription model or stop using adblockers. Good luck to everybody else ...