You're talking about payday loans versus cashing paychecks. It's usually a token fee to cash a check at a grocery store or free if you go to the bank that issued the check. Some people live by cash. Some businesses still operate on cash only basis.

Some, not most. And each continues to dwindle over time. Privacy is a human right, physical currency is not.

All you have to do is look at prisons as a good example, standard currency is tightly controlled, typically not very available to inmates and somewhat pointless to inmates anyway. So alternative currencies are used. Drugs, cigarettes, food, weapons, personal hygiene stuff, people, the list goes on.

Currency is only as meaningful as its usefulness to people. If a large number of people can't or won't use a currrency, they'll just find another. It wouldn't be the first time in history a majority currency became too inconvenient for a large number of people and alternatives were found.

It’s very likely the majority use the currency their government pays them in and requires citizens to pay taxes with. Alternate currencies will always exist, governed by the needs of market participants.

See this attitude is why I'm long on cryptocurrency.