The thing about the "I need cash in order to do things the government doesn't want me doing" is that it's just incredibly precarious. Very difficult to use that as an argument to government or its supporters. And it tends to "evaporate" over time as people stop using cash for "legitimate" purposes. So you end up with nonsense like US asset forfeiture, where the police can simply steal your cash.

> mandating any merchant of goods or services to accept cash

The fewer people actually use this option, the more likely the merchant is to be very passive-agressive about refusing it. Like claiming not to have change.