Do you really believe that the CC rewards are free?!? You, the customer, ultimately pay for them. Purchase by CC costs the merchants money (how much is it nowadays, around 2-3%?), the merchants pass that price increase on to customers (regardless whether they pay by cash or credit card nonetheless).
By that logic then it makes even more sense to use the credit card over both cash and <whatever>coin. If the transaction price is getting bundled into the overall price of the article I'm buying, why would I pay in cash and lose credit cart protections and loyalty points? Or even worse, why would I pay in bitcoin and lose the same as above and incur a transaction fee myself?
Which they don't and also it's illegal. You can charge less for cash, but no one does that. (Except your one or two examples out of the thousands of stores)
It's not illegal, but it is against Visa and Mastercard's rules, to levy a fee or surcharge to use a credit card. What IS illegal is to prohibit merchants from offering a discount to induce customers to pay by cash or check, which is why merchants that do so don't end up having their Visa and Mastercard contracts cancelled.
