Governments serve a basic purpose - To help the community grow and prosper. They have a singular function of serving the needs of the community. Now taxing cryptocurrencies is very hard but there is also an understanding by the Blockchain community that funds for public good is required. The most simple way to tax cryptocurrency traders and developers is to make taxation voluntary and on chain. Once you know that the transaction is on chain you can go ahead and track the end beneficiary of your money and there should be an option to choose your money to be given to local / national cause along with certain restrictions. I think taxation can be DAO in totality and this has been the major idea behind DAOs.