True, they could..good point. Although, that would be a complete reversal of the trend we've been seeing recently where governments are adopting legislation for Bitcoin (ie, https://www.cryptocoinsnews.com/south-korea-preparing-legalize-bitcoin/ and http://www.coindesk.com/illinois-blockchain-initiative-policy-regulation-bitcoin-blockchain/).
True, you never know how things might change in the future, but in my opinion the popularity of Bitcoin and crypto is growing at such a rapid rate, even though you're right governments could go to extreme measures to shut it down, it would be politicial suicide (at least at this point) to publicly take such drastic countermeasures.