There are a couple practical reasons why they wouldn't want to: high risk of fraud or chargebacks and difficulty keeping on top of content that veers into illegality spring to mind immediately.
Like paying for abortions or gay weddings in certain states? Buying cannabis from somebody on the street instead of somebody in a store 6 months later? Promoting unions depending on the decade? Letting “trespassing” black people buy coffee in shops that banned them in the 60s? Making breaking the law impossible is dangerous
This is a very legitimate concern -- payment processors could start enforcing that kind of thing based on morality.
However, unless something has changed lately, for decades the issue with adult content + online payment processors is not morality related. It's because of the high fraud/chargeback rates associated with online porn transactions.
Unless it's SESTA/FOSTA related, but I don't think anything's changed on that front for a while.
They can simply charge more based on a mathematically provable risk of fraud/chargebacks. We can regulate that to make it fair/transparent, and also regulate that payment processors must not discriminate against any activity that is legal.
Yeah, this is a fair point. I think it would make sense to require them to offer services, but let them charge a rate that allows them to make similar margins as on other business.
