Most of the government system today tries to regulate the usage of Bitcoin but they can't and will not ever regulate it. They can adopt it as form of payment for faster transcation. I believe in the near future most countries will adopt digital currencies.
The thing is governement control or try to control people and tax them. With bitcoin they got 2 reasons reasons to control bitcoin.
Which makes bitcoin vulnerable to new regulations. As you can see many governements already tax bitcoin income.
The government did not tax Bitcoin. They only tax the cryptocurrency exchanger, the user of these exchanges and the cryptocurrency miner. They are the people need to pay the tax, if you are only a holder of Bitcoin, no one know you are holding it because the Bitcoin system is private system. You can know the amount of Bitcoin in an address, but you do not know who one has that amount.