Given that it is within the power of the Chinese Gov, to ban or at least ban all Chinese companies from dealing in Bitcoin, why have they not simply banned it?
How could they ban it and under what grounds? Even if they did 'ban' it, it's not going to stop people from using it.
When countries have severe hyperinflation they always ban the use of foreign currency and everyone keeps on doing it. At some point people are pushed far enough that they perform civil disobedience.