because like, those exist, I've seen payment gateways branded by a specific bank and stuff (that wasn't mine). hell I used to work managing a bank's API designs and they were there. are those really that expensive and complicated?
(you never actually getting to know how much do some of its products cost or how does one access them is one of those weird things about working software for a bank. you just build it and someone else will take care of making the money flow)
@kitten a lot of them don't do adult content either (but theres an entire cottage industry of processors who do, who, you know, process for all the porn sites)