Because it's Visa and Mastercard saying no, not the banks.
I suspect they are currently not classified as adult and the banks are saying, look, you are almost entirely adult so you have to pay us more.
Besides PR in the age of revenge porn, what's the technical or legal element which changed compared to 2019?
Can't be social because if anything society is in love with porn.
For some reason payment processors have always viewed themselves as morality police.