They'd be walking straight into a trap where it would be checkmate to crypto if they tried to do that.
Something that gets overlooked quite easily in all these discussions is that nobody actually "owns" any crypto in any legal sense. The only type of cryptocurrency asset they could possibly regulate would be exchange traded funds (ETF's) because there is a legal contract there saying you own it.
Look around you at any person's significant asset portfolio - property, contents, car, inheritance, stocks, bank balance....every single thing of any significant value is governed by some kind of documentation where the legal system is the governing counterparty.
A blockchain address is not owned by anybody. You happen to know the private key to one or two, but the fact that a few people have the keys to my house doesn't make them owners of my house.
So all this talk of 'banning' is slightly mute. The 'trap' is that authorities would have to go to such lengths to legitimise cryptocurrency as money in order to get anywhere near regulating its ownership in the statutes that they'd just be boosting its valuation to kingdom come and increasing its profile as a store of value.
The nearest precedent I can think of is the prohibition on holding gold in the early 20th century. That was almost unenforceable even with bits of physical metal. But try coming round someone's home and searching for a set of private keys to a bitcoin address that don't respond to metal detection and that can float away up to an encrypted image on Google drive in seconds - it's a non starter for enforceability even if by some miracle physical possession of private keys found its way onto the statute books as a definition of 'ownership'.