Look at what's happening in Nigeria [0]. They have tried to ban bitcoin, but are now looking to legalize it. It's just too difficult to enforce when a lot of people are doing it.
It's too difficult for Nigeria to enforce. Nigeria has a very weak government that has trouble enforcing a lot of laws that other states have no trouble with. OP mentioned Russia and China, and I would be very hesitant to extrapolate either country's capabilities from Nigeria's.
I will say that this could be a valid use case: if you have an ineffective oppressive regime, you may benefit.
[0] https://bitcoinmagazine.com/legal/nigeria-looking-to-legaliz...