It's not banned just because of tax evasion and such. Governments are not inherently bad, and the system is not just out to fuck the little people. If a real economic bubble occurs, the governments want to let it down as soft as possible. Crypto is a bubble, and many coins will crash and burn due to the lack of regulation there is now. This will cause many people to lose their homes, life savings and might even cause suicides. Some people will get rich, yes, but that redistribution of wealth is not good for the society. A good government should therefore try to manage the investments a bit, so that the bubble can not grow forever.