Many Chinese citizen is already using bitcoins or other crypto coins to make profits and make some sort of payment in the form of digital currencies. But I think China bans all type of crypto transactions because the government itself can't profit much from it and because it is decentralized, they cannot oversee what is exactly happening inside and the Chinese governemnt cannot act as a middle man and have that authority just like any other banks.

Sure China is making a lot of fuss this past few years and they have been making moves arbitrarily and make some countries mad about their system but we can't do anything about it because they even don't care about the international law.