Lot of countries do not allow to use crypto currencies and they discourage using them. However as far as I feel, trading with crypto is not that harmful for the economy of the country. As an example, if a person has Eth and someone from another country needs to buy Eth, that buyer needs to pay the seller in terms of dollars. Then that seller needs to convert that Dollars to his native currency which means it creates a the demand for the native currency and increase the value of the currency. May be the government is unable to add a tax on such transactions but it is beneficial for the currency used in seller's country.
What do you think about that?
Your thinking is aligned with a tax-free economy and competitive. Exchange in all markets is always accompanied by taxes. Taxation is the source of government revenue, if bypass the government tax will not be able to survive