Are you sure of that?
Since if you are and the government is really going to accept Bitcoin as a means of payment for public services, that basically means that you can pay taxes in Bitcoin directly. Taxes (as you yourself imply) by their very nature are the payment for such services (i.e. "the source of money to keep infrastructure growing"), and paying taxes in some token effectively makes this token into a legal tender since the definition of legal tender is exactly that, i.e. a means of payment for all public debts, taxes, and duties
The only way governments would be able to tax Bitcoin is if they do what you just said - require payment in Bitcoin directly. Otherwise good luck trying any other method. And someone just proposed they tax exchanges. In my view this is actually the best option that governments have at this point as they can track each person's trades and tax based on that. Everyone would need to upload their IDs and such and have one account only per person.