Yes, this is true.  While it is true that Cryptocurrency brings a lot of positivity and power to back to people, making it decentralized - it is also true that its risk of dominating the world in the hands of evil people will prevail.

When a country sees the threat of allowing cryptocurrencies to dominate the nation, they can completely ban it. Another thing to realize will also be utilizing other potential inventions which are at least greater than cryptocurrencies without thinking of the casualties.

Another important reason will be authority and sovereignity. Countries will ban crypocurrency because it threatens their power to rule. Cryptocurrencies are meant to be decentralized and will forever be. I can sense that with the direction of cryptocurrency is going, there will always be countries that are against it.