Even if people like it or not, only having cryptocurrencies instead of fiat would sadly never work in real life. I dont really understand the point either, each of them have its perks (Fiat/Crypto). Specially in the case of fiat cash which does not need the internet.

What would happen in the future if your country enters a war and you have no access to internet? You are doomed. I think having both is a great advantage!