Tax is a need that must be obtained from a transaction carried out in a country.
Yeah sure tax is needed and important because is the only way to improve the state of the country.
Therefore, transactions using bitcoin must also be taxed. But the problem is that all transactions occur in cyberspace, so the government cannot control it.
Transaction of bitcoins does not occur in a cyberspace but they only occur online under the blockchain system/technology . you can still pay your own tax if your government cant tax you because they cant hold bitcoin .
Therefore, the government must be aware of the final transaction, namely withdrawal of cash money on the exchange of bitcoin because that is the only chance the government can withdraw taxes.
Some exchange are centralized , i think governments can carry out a tax on them . there are also local exchange available for crypto to fiat withdrawals , this might also be possible for governments to charge them/us by a tax .