> Because merchants charge everyone the same price regardless of how they pay, those fee costs are factored into prices for all shoppers. However, credit card users get that money back and then some through rewards, while cash and debit users get little or nothing.

And they charge everyone the same price because credit cards contractually force them to. Merchants can either accept these terms, or forego credit cards entirely. This way credit cards prevent other payment methods from competing on price. Free markets for thee, contractually forbidding competition for me.