Because they are afraid to take risks, they think that the bubble can burst at any moment. And the state wants to control all financial operations.
They are not afraid to take risks, bitcoin helps a country economy, and I don't think it's price matter at all. Bitcoin is a decentralized digital currency so they can't control the bitcoin transactions. There are many reasons that the government are not accepting bitcoin, but I know time will come and they will be changing their minds when they see how bitcoin helped other country.
Yes. Government is afraid of bitcoin for being decentralized. So they can't control it. That's why some government has put a strict regulations, while other doesn't want it in totally, while other like Japan see it as the future of technology that's why they make it legal. But I know that maybe in just a few years we will see that some big government globally will accept bitcoin as alternative to the common fiat.
Perhaps in the future, and take bitcoin if it does not fail, but it will be an additional currency.