Processing cash might cost retailers even more than cards (miscalculations, keeping change, counterfeit bills, cash collection every day) unless it allows them to evade taxes.

Unless there were some sort of government-provided zero fee digital system for money transfer. Oh well, surely such a thing will never exist.

Not sure if people who prefer to use cash will consider that an adequate substitute.

Well for corporate stores yes. Still a good number of rural area small businesses that give a discount for cash, or only accept cash.