Government has been relying on tax to growth its own economy. Though tax, it is able to maintain the country and provide infrastructure and government services like schools and roads and buildings. With bitcoin, it does really pose a risk for the government.
True, governments wants you to pay your taxes, because sometimes they need that money for doing things for like roads and stuff. If i was the government and i saw you not paying taxes with btc.
I would surely do something about it. Maybe even disabling bitcoin for a limited time to make them scared, but we are lucky that they are not doing this.