Is processing payments for porn sites so much different that companies that specialize in it exclusively are needed? Why can't a company like Paypal or Stripe support those merchant account classes and procedures?
It's all about the rate of chargebacks and fraud. I would hardly be surprised if your average porn site was subject to both frequent chargebacks and heavy use of stolen credit card numbers, if not both at the same time.
That and association. PayPal just doesn't want their name associated with stuff like that. It's hardly limited to just porn. Anything remotely sexual is rarely sold via PayPal or a major non-Adult-oriented payment processor.
