This could be true but the government could not expect that its constituents will going to abide the ban process for it will still be able to access some of the exchanges outside the country. As we all know that there are online payments now that could be use to purchase cryptocurrency so people living in that country where cryptocurrency is ban could still enjoy and participate in cryptocurrency.
There are several reasons behind this ban of cryptocurrencies.Cryptocurrencies are not under the control of any central bank or government as they are decentralised and even taxes also cannot be implied on cryptocurrencies.Cryptocurrencies are risky as they can get hacked too.Cryptocurrencies are require internet connection which is not possible in every corner of the world therefore it is less supported in the market internationally.