> A lot of problems would go away if all merchants (voluntarily or by law) explicitly charged their payment costs to the customer.

At least in the US, the contract the retailer signs with the CC processor to be able to accept CC's explicitly bans passing the card fees on to the customer as a specific line item in the receipt.

Which really translates to the merchant increaseing their prices by 1.02x to compensate for the 2% (avg. estimate) fee the cards charge. So the customer still pays, but they do not directly see what part of the price goes directly to the payment network.