In some countries, maybe. In the US, there were concerted attempts (like the First Amendment to the Constitution) to prevent that from being the government's job, because of the fear that government would use that job to suppress dissent and coerce opinions.

If payment processors are picking up that job, and doing so in a coordinated manner that doesn't allow porn companies to simply say "use these payment rails to do business with us, not those ones," it is not unreasonable to suspect that they are doing so not for their own business interests but as a proxy for powers that the government is denied. Someone should be taking a long look at whether the US-based payment processors are becoming a tool of censorship and, if so, how that censorship is being coordinated. It's not like Visa and Mastercard come up with these things independently and on a whim.