Not only would the 3% fee not make me blink, as my cards have 3% cash back for dining, I doubt I'd change my behavior even at a 5% discount. If anything it'd dissuade me slightly from patronizing the restaurant.

Credit cards are convenient and cash isn't. The genie is out of the bottle, no way to make people move back to cash.

You're not the avg person though. Most people are being squeezed by inflation and watching prices on everything and trying to claw an extra 2-3% back wherever they can.

If interchange fees were capped, people would go back to cash, imo. A lot of research shows you spend less when you pay with cash. And the lack of credit card rewards as a draw might lead people to carry it again