I'm wondering this because is such a real threat to bank system and we all know how banks and governments are tightly linked !
BTC could make people more autonomous, self-resilient, being their own bank. You can use it like cash, making your transaction almost untraceable (or untraceable using e.g. monero or dash or laundry systems) : this is governments worst nightmare, isn't it ?
Bitcoin system has iy flaws. The value is very volatile and sometimes a big drop occurs. I think the government is just cautious on bitcoin to be legalised. They are always concern of the people safety and the security of there money.