Because the credit companies are acting under the guise of the law. "I don't want to end business with you, but the law compels me to do this!" If you haven't broken the law, there's no way to appeal this decision they've made as they do not have a route for that.
That aside, the ability to pay a service is pretty much fundamental to its existence. Being able to at-will terminate any company you want, even ones that are provably innocent, with no way for them to so much as appeal against your decision is a worrying amount of power for a company to hold. I don't think that even the government can do something like that (at least not legally).
The law tells them who they can do business with, and they comply. That's not really a guise, unless me driving the speed limit is also a guise... If there's any challenge here, it's that such law restricts card networks' freedom of association. Which the US only has as an extension to freedom of speech... So I'm not sure that challenge would work, when the entire point is that certain forms of speech are what's being limited.
It's a guise when the law is not actually what motivates their decisions. Like if you used the speed limit as an excuse not to go to a particular grocery store, or something.
So am I understanding correctly that your assertion is that the card networks actually don't want to do business with these companies, and they use the law as an excuse?
I find it the claim that they would rather not do business with entire multi-billion-dollar markets pretty exceptional.
Mostly yes, my claim is that they don't want to do business in many cases, largely because of widespread taboo and because of worry it will make them look bad. Companies are made of people, and the latter does have financial consequences.
But my claim isn't that they want to avoid the entire industry. It's that they want to cut certain segments and use their control to make things as 'tame' as possible. So that actually doesn't cost them very much.
That aside, the ability to pay a service is pretty much fundamental to its existence. Being able to at-will terminate any company you want, even ones that are provably innocent, with no way for them to so much as appeal against your decision is a worrying amount of power for a company to hold. I don't think that even the government can do something like that (at least not legally).