Even if you use Bitcoins directly (for supermarket purchases, utility bills, buying gasoline.etc), it can be taxed. The government can just ask the retail chain to impose a surcharge on the Bitcoin payments. So if you are paying with BTC, there will be a 2% or 3% surcharge, and this amount will go to the government as tax.
Interesting point dude.
Some governments and countries recognize Bitcoin but they make a regulations that they will benefit it like inputting taxes from exchanges.
In such countries, there are a variety of taxes. The exchanges have to pay corporate taxes on their profits. The users have to pay VAT on their Bitcoin purchases, and capital gains tax on their profits. The employees of the exchanges have to pay income tax on their salaries, and the company will have to pay labor tax and the social security for the employees.