That's like asking "what does rent have to do with property prices?". Just because you've managed to be on the top of this perverse social summation of usury doesn't mean it isn't predatory and a net negative for society.

Credit cards are one of the most insidious ways that banks extract money from those living closest to the margins of poverty. The benefits you gain are a fraction of the profits gained from raking the most vulnerable over the coals of bankruptcy. They're a financial instrument of torture and I refuse to have anything to do with them. I'm not by any means rich, but I'm 48 years old, have zero debt, and will spend the rest of my life avoiding debt.

Finance is not a zero sum game.

No it's actually like asking what cars have to do with debt. You can have a car without going into debt just like how you can have a credit card without debt.

Since you have such high moral standards I hope you don't invest in any index funds because lots of companies in those would probably not live up to your standards

It has been legal for sellers to ask buyers to pay more if they use a credit card for 15 years now.

There is no "moral" quandary. Sellers that have the same price for credit and non credit payment methods are simply betting that people using credit will be more willing to pay higher prices overall and still buy from them compared to their competitors' with lower prices who charge more for credit cards.

Every year, fewer and fewer of my expenses are paid with a credit card because more and more sellers are not betting on this. My kids' gymnastics class/tutoring/daycare charges 3% or more for credit cards. My home wired ISP and mobile network provider charges 5% more for credit cards. My property tax, insurance, water/sewer utility, all charge 3% or more. Even Target charges 5% for credit cards. Basically all tradespeople that come to fix things on my house charge extra and ask for Zelle/Venmo electronic cash payments instead.

So in all these cases, I do not use a credit card to pay. But the point is, it is up to the seller to decide what price they want to charge for credit and non credit, so there is no "moral" quandary for buyers. No one's hand is being forced.

Edit: to respond to comment below due to hitting posting limit, the extra charge does not go to the card issuer, the seller collects the higher price. If I choose to pay with a non credit card payment as a result of the extra charge for credit cards, then the credit card issuer gets nothing.

Whether or not credit card interest rates and terms are usurious or otherwise morally problematic is not a credit card user's moral responsibility. When I use a credit card, I do not ask or enable or incentivize someone else to be taken advantage of.