Countries who think that bitcoin is a big threat to their economy are the ones who ban it. Countries like China, Thailand, Vietnam, etc are the ones who already did. But I think it is nearly impossible to totally ban it in their country. People who already made a lot from bitcoin will always try to access it even though it will be illegal. The very easiest way to ban bitcoin is by cutting off the internet access of the country which is probably impossible. Banning of bitcoin is due to its negative side where it can be used for money laundering, black market and tax free transactions.