You actually did not give strong reasons why cryptocurrency can't replace fiat currency. Cryptocurrency can actually/theoretically do most things fiat currencies can do, but I doubt typical fiat currencies can safely do most things cryptocurrency can do with losing their centralization. Besides, government can run their fiats on Blockchain or other real decentralized system.
Crypto could actually work better in rural areas than fiat, even without relying too much on internet. But I believe safe/crypto-friendly worldwide rural internet coverage is a possibility in the future
yeah exactly. "it will be hard to adopt" is not the real reason why cryptocurrencies won't replace fiat its an excuse not to work hard for the result imo.
I see only one reason why crypto can possibly not become next fiat - people's skepticism about crypto and blockchain overall.
But honestly I think its a matter of time when most of population will understand and accept digital currencies.