17 years ago, my business partners and I were approached by a porn website looking to get their website redone. (We didn't take the job, but it was an interesting meeting.) He said that his biggest problem was "refunds".
It seems it was a common thing for people to buy his service (access to porn), and then a few days later claim to the credit card company that it was an unauthorized charge.
He told a story of an irate wife calling him on the phone one day and demanding the charge be taken off her husband's credit card bill. She was insistent that there was "no way" her husband would sign up for a porn website. Well of course he did (or was it their son?). But he couldn't admit it to his wife. And so she called the office of the porn website to complain.
I'm sure that hasn't changed 17 years later. Credit card chargebacks must still be a huge problem.
Chargebacks make it a customer service nightmare. One of the highest refund rates that credit cards get, the highest incidence of actual fraud (charges that really weren't authorized), undisclosed recurring charges, etc.
Still, cutting off service to the models seems unfair. But refusing to deal with the websites themselves actually has underlying business reasons other than morality.