This is why Bitcoin is better than banking system, it's faster and transparent, there's no hide or secret fee if you want to send a coins. Government will not want to accept Bitcoin as a currency because people might tend to choose Bitcoin over their fiat and banks, if not many people use fiat and banks, the government will not make a lot money and many banks will collapse.
Mate, OP was not wrong in calling them Crypto currency. Bitcoin is still under the Crypto currency classification and it is a blockchain on its own while shitcoins just as you have said are the altcoin or tokens that liverages on other blockchain to sustain their scalability.
No doubt bitcoin is the most popular Crypto currency in the world and has gained traction for itself since it's inception. However, bitcoin and Fiat are unique in their own ways so therefore, non of them can be sidelined to function in the capacity of the others with the rate of the current situation of their existence.
Fiat globally is the government number one recognized legal tender approved by them but bitcoin is a digital asset yet to be recognized and approved by most of the government globally for the fear of their local fiat being neglected. The fears of the government are too many to accept bitcoin in place of their currency digitally.