Because bitcoin threatens the status of paper money in my country.Bitcoin is not controlled by any person or any government,also bitcoin is always used for illegal activities,so the government banned it.
It doesn't threat the paper money, it's been considered as a threat to the paper money by the government's. This is completely wrong and in few Countries when bitcoin usage increased the local fiat value went down. This too was considered as a threat and in such a way each country have different reasons to oppose bitcoin.