Government can't kill bitcoin because government has no full control in bitcoin because bitcoin is a decentralized digital currency. Also, maybe you have a point, maybe government officials own also a bitcoin secretly for their own or they invest into bitcoin to support the economic financial system because they know bitcoin is a good investment nowadays. Nobody know! But the important is we are free to use bitcoin and other crypto currency.
A government can come up with rules and regulations that it could make things difficult for a user. If they force the exchanges to shut their doors and ask the credit card companies to never deal with cryptocurrency then it will be difficult to make trade normally and any government could enforce these rules and if they declare huge punishments then who is going to take that risk. So it is possible that a government could make restrictions.