I agree to the first part, they are not willing. They are also starting to embrace the technology, not much the currencies and it makes sense.
But how could they stop them? I am curious technically speaking. Making them illegal and closing exchanges might give them strength after an initial drop. Btc had already two massive corrections, it's heavy in mining, slow in transfer and expensive in fees, but still breaking up and being stored even by some top investors.
Government action would make sense for crypto like xrp-ripple, as they are looking for acceptance in the system, and they do offer speed and cost never seen before.
But most crypto seem to love their decentralized, whatever legal or not status. Btc first rally might have been pumped by the all dark web illegal business and easy hidden capital transfer.
Governments can probablyly act on their value but I don't see how they could take blockchains off the net so easily.