The governments can't control Bitcoin because it is decentralized. It wasn't made in favour of a centralized system where one person or authority can have full power and control over its transaction. The farthest the governments can go is to impose regulations on Bitcoin transactions especially on the exchange sites.
Your first line of thought or statement is the perfect answer why government can't control Bitcoin; decentralization is the main reason which has lead to the high trust found in Bitcoin. But as for other altcoins, or maybe a good number of them, they can be easily controlled because even the team cares for themselves first. Also, although there many altcoins which claims to be decentralized, however it is important to know that only few are actually decentralized or somewhat decentralized, while others are just hiding under the claims of decentralization just to exist and keep working.