The government has never been able to enforce all laws even close to 100% of the time. Internet copyright violations never went to zero, and never can. But there is a ceiling on how far any large, organized profit-seeking group can go with it.

In the case crypto, there are lots of things they could do to limit the impact. They can forbid government regulated banks (or any corporation) from engaging with it. They can limit all the points where could you, in volume, convert in and out of the normal currency system.

So, obviously, the use of crypto can't be forced to zero, but that's not really an interesting point.

The question is, does crypto have, on balance, a legitimate use in developed liberal democracies? Or should these states suppress it?