Think of it from a government perspective. The government knows about the good uses, but have to weigh benefits and disadvantages. The disadvantages are million-dollar black markets. The original silk road itself used to comprise a large part of bitcoin's market cap back when it was still in operation. It handled more than $20 million dollars in trades. There are now above 50 dark web sites using bitcoin and other cryptocurrencies. A person who gets money from running masternodes, using steemit, etc. can search up "stores that accept cryptocurrency" and use those to purchase things like lysergic acid(used to make LSD) or hydroponics equipment(for growing weed indoors) anonymously without the government having an idea of what kinds of illegal things he is doing. He can buy guns with bitcoin online and he can shoot whoever he wants, and the government won't even know he bought a gun. There is this same problem with cash, but cash is restricted by physical location. Overall, I think cryptocurrencies are good and should be completely unregulated and untaxed, but this is what governments think about cryptocurrencies.