Fiat currencies definitely aren't necessary, there is an increasing trend towards digitization of currency, and blockchain based currencies are just the next generation of this. The problem is that Bitcoin came out, and everybody treated it as the successor to fiat currency, rather than an incremental improvement on digital currencies such as Paypal and Skrill. I think that if Bitcoin was never invented, but somebody like Paypal had implemented a blockchain technology first, then we wouldn't be in the rivalry scenario that we're in now.
It has some point. It is a stereotyping in which we tend to believe what we have commonly seen, or somewhat we believe the thing that we just assumed. This kind of mentality is probably what most of the cryptocurrency users needed. We must not only considered our personal interest but rather think of the future benifit of everyone. But still it will be benificial if everything will be digitalized because it is the new trend and what people need.
but not for now. and that happens for future. we can see, currently many countries are not ready to accept digital currency, and for that requires a process, because each country has a different background