China has not banned cryptocurrency. They just banned ICO and exchanges. Peer to Peer trading is still available and actually quite popular in China. I don't think there is an effective way for government to ban bitcoin anyway.
Right, government cant ban bitcoin easily because they need this technology. Government may regulate bitcoin but for them get some taxes, government will find ways just to control bitcoin that can never happen.
Government need to find methods to control bitcoin because government need this kind of technology. They don't have rights to ban Bitcoin easily because they do not know how it function and how Bitcoin is all about. Government should find first the effective way to get the advantages from Bitcoin