Fiat money were of no use in the Ancient Egypt as well, but now they have about a 1000 years of history. Banks are sometimes using 50-year old code. Bitcoin is only 7.5 years old.
Since the age of empires (the classical period), the monetary items to be used in commerce have always been under state control, because who controls the "blood of the economy" controls essentially everything: you make the riches and the poor, you pay armies and traitors and it happens essentially in an invisible way. Even gold and silver was a kind of "fiat" during the Roman times, because their conquests served essentially to take slaves, and to open silver mines that financed the state and its wars.... to conquer more territory, to obtain more slaves and silver mines.
The European nations did about the same at the end of the middle ages in America with the gold mines over there. So even gold and silver have been "fiat" money, in the sense that they served as seigniorage financing of the state. Next came of course diluting the precious metals in state coins. The Romans did it already. Fiat money is simply "infinitely diluted gold and/or silver". The dilution reached infinity in 1972.
States will never allow a monetary asset that they can't control as the main blood of the economy. So forget the idea that you will LEGALLY have bitcoin as a general currency - unless - and that is my hope - that it sneaks in and takes states by surprise, weakening them, and in the end, make them collapse. States can't live without pumping money. They are the parasites that need to drink the economy's blood to survive. They will not allow foreign blood to flow in the majority of economy if they cannot make it, control it, and take it away at their whims, unless they have been weakened enough that they lose their power.
Bitcoin is a totally different beast than any other state money, whether it be gold or paper fiat, in the sense that bitcoin cannot be state controlled - unless China seizes all the mining, and bitcoin becomes Chinese money. It will never be accepted by states as a currency.
At best, states themselves will invent some kind of state crypto, of which they get the seigniorage, they get to decide upon the forking, and they have the exclusivity to mine/mint/print it. At which point it is not a free crypto any more. Bitcoin could be state-forked into such a thing. But it won't be bitcoin any more.
It would be a freedom nightmare: a compulsory blockchainish state currency, somewhat monero like, but with a state golden viewkey, so that they, and only they, can see every transaction.
If you want to call that "crypto", be my guest.
