That's because paper currency are believed to have value and are also legitimate by the government, so paper currency can be used to buy all your needs. Not because of the paper, but because of the approval from the government and also a belief that it has value.
what you convey is very true not only crypto currency paper if the government has legalized it and approved the crypto currency as the official currency I think the crypto currency will be held
right, the government does hold the key to being widely used. without the approval of the government, i think the development of crypto as a currency cannot develop as expected