While a government system that makes electronic money transfer a utility should exist, the real benefit of credit cards for merchants is that credit card users are willing to pay a higher price and thus catering to credit card users results in more profit. This is evidenced by the fact that all major merchants do not offer discounts for using debit cards/cash, with the exception of Target. But even Target does not make it easy, you have to sign up for a Redcard and link your debit card to it.

Merchants that do not like credit card processing fees already stipulate card purchase amount minimums or discounts for cash/debit. The merchants that do not evidently are betting that more money can be made from selling goods at higher prices to credit card users.

Of course Visa/Mastercard offer debit, but even with FedNow, I suspect many merchants, especially the biggest, will continue to want buyers to use credit cards, and hence support Visa/Mastercard/Amex/Discover.