in my opinion it is still a bit necessary, what if you got somewhere and there is no internet or electricity but you still need to pay for something?
if there only were cryptocurrencies for wich you need internet to send a transaction then you would be stuck to buy the thing that you would want or need in that situation
Seeing that there are no fiat options that can be used anywhere and as easy as using Fiat, then Fiat will be very needed, who is the best fiat currency option? crypto? crypto certainly has not become a mainstream, many people still don't know it, fiat is still not replaced