Digital currency is to change the world, many of which were positive, to a certain extent, they pose a containment of the government, gave the people an alternative, but that doesn't mean they don't need to be regulated.
One of the core reason is: anonymous, do not track, not regulated digital currency will make form a closed loop technology crime, money laundering and terrorist, and disappear from unsolved bits, bytes, while the impact damage with each person in this world.
If every penny of extortion is tracked, is there enough motivation and courage to launch a WannaCry to attack the world?
I think one of the concerns that the government and banks have with digital currency is that they are anonymous, in which can be used for money laundering and fraudulent purposes. Yup, it's true because Bitcoin is decentralized. It is why they want to regulate Bitcoin because they cannot control or stop it. Just my two sats.