Before the existence of bitcoin they're many other digital economic assets that is in line with government policies like crude oil, gold and much more, government where comfortable with this assets trading online, including forex but crypto currency like bitcoin that would have change lives and alienates poverty from the world, government are afraid of its cumulative value.
Those assets can easily be controlled by the government and they can monitor them which is why the governments didn't have any problem with them been traded online. Bitcoin is different, Bitcoin is decentralized which means the government can't control or regulate Bitcoin which becomes a problem for them and that's what they're not allowing Bitcoin to grow.
The government wants control and they'll only allow what they can control prosper like centralized digital currency and try to kill other's although all their attempts to kill Bitcoin has failed and that's why we're now seeing some government officials now accepting bitcoin.