Re: The folly of individuals notwithstanding...
It's only true to a point though. I do know of credit card providers pulling the plug on people who gamble "excessively" and not reinstating them until bills are paid and proper assurances received.
At the end of the day, like it or not, a credit card allows you to spend someone else's money. That someone else therefore is allowed to say what you can or cannot spend that money on. And who knows, maybe this is the catalyst which drives credit card providers to stop people from using them in book makers or casinos*.
And it's worth reinforcing that no-one is stopping from spending your own money on any crypto-transation that you want**
* A perfectly reasonable idea in my opinion
** Or potentially your gambling