Usually it’s not stolen credit cards, usually it’s their card but they say it was stolen and try to do a charge back.
Hubby pays for porn.
Wife looks at bill.
Hubby denies it, must have been identity theft!
They demand a charge back since clearly card stolen by unknown porn hound, not innocent hubby.
CONSEQUENCES
Card processors and especially customers of card processors get their accounts flagged for too many returns / charge backs, which cost much more to handle than the original transaction fees compensate for. Rates go from a couple percent to 20%, making business models not work.
Banks that the processor deposited into when card swiped, have to risk manage how much money to hold back from the customer in case 2 months later all the deposits get sucked back out by charge backs. What happens if the bank customer had withdrawn their money?
BAD OUTCOME
Very hard problem, easier to just not deal with sectors that have extreme and unpredictable charge backs.
I suspect it's just fraud, people using stolen credit cards and bank details to pay for porn (because porn can be delivered digitally)
So these accounts disproportionately show up in the fraud department and the fraud department spends more time dealing with those accounts than the profit generated.
Eventually, the bank or payment processor decides it would be less effort just to get rid of the customers causing issues. The moral questions probably means nobody internally feels like defending them.