Because the government still considers Bitcoin as a tool for money laundering and wants to control it.
It's not a crime if they're laundering money. It's their money, they can do whatever they like, but you are going to be put in jail for doing the same thing.
In China you can be put to death for counterfeiting money, which is one of the most bizarre things in the modern world. They print money, but if you do the same they'll kill you. They pretty much remained in the middle ages with laws.