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.
Apart from your statement above that Governments cannot control Bitcoin and is designed in a decentralized manner, the government should also be aware abaout what potential can bring feedback, both taxes and others for their respective countries along with the rules and regulations of restrictions that will be set for they country.