If you are very conversant with the news, the common reason why different government have ban cryptocurrency is because people use it to transact illegal businesses and because of the high fraud rates. If fraud can reduce on Bitcoin and other cryptocurrencies, the government will most likely lift their bans or if the government finds a way to catch illegal transactions made on Bitcoin, they will likely lift their bans. Again, the bank industries are threatened with how crytocurrency is getting wildly accepted and they are getting scared for their business. As the central banks of most counties are run by their government, the government have to protect their interest and impose these bans.