Crypocurrencies are banned because they are an independent store of value, which is not submitted to fiat money inflation.
In my own opinion, cryptocurrencies are banned because there are some governments who are corrupted since bitcoins and altcoins is one good investment which another way to make money on the internet.
It may happen, but in many directions the country is still in the process of learning about it. And there are still no consensus on the idea. Maybe they are scrutinizing then making a decision. Hope so.