Because new things come out, it will take the place of some old things. BTC they can't control it. They can only be destroyed. They like to control.
Controlling the economy is the big threat of bitcoin in any country, with how bitcoin works it will be an easy access to bypass taxes and if that will continue then it can break government system, if more people will use this system then the country will suffer, I think proper knowledge and better understanding is really needed to ensure the stability of any system that will be introduce.