Authoratarian regimes (like the CCP in China) would never want the people to be in control or power to be distributed among the masses. Something like Bitcoin or decentralised ledger is a threat to that idea itself. And even Democracies like US, because of the existence of taxation etc, they like to think an alternate payment system is a route for tax evasion, money laundering etc.
And by the way, I'm talking the specific case of cryptocurrencies serving as an alternate payment method. I assume most countries have taken a positive stand on the underlying blockchain technology.
Well said. Totalitarian governments have more to lose from people switching to cryptocurrency than democracies. That's why the Chinese government has encouraged companies like TenCent to improve non-cash transactions. This have the additional benefit (for the gov't) of being able to track what people are using their money on. For citizens it basically fulfills the ease of transaction bitcoin promised minus the chance of gaining a profit (though no profit is worth it if the CPP decides to go after you anyway ).
With democracies the main fear of the government is losing funds plus the loss of control over the financial system (they've reserved the right to mint for themselves as well as regulating banks, etc).