Actually most states do permit credit card surcharges by the merchant. California, Colorado, Connecticut, Florida, Kansas, Maine, Massachusetts, New York, Oklahoma and Texas are the ones that ban it. Some of those states have pending litigation against those laws. Some of them also allow discounts for paying cash (as if it's any different than a surcharge for processing)

There was a time from 2013 to 2017 that merchants were permitted by processing agreement to do it, but Visa and Mastercard convinced an appeals court to throw it out. A few places in my state still do surcharges, but it's pretty rare.