This is one of the, if not the most, important levers it has to wield power. Governments have fought wars and enslaved entire continents to protect and increase the value of their means of account. Even recently, think of how hard the US works to maintain the dollar as the only currency that can be used international oil transactions aka the petrodollar.
Ultimately, cryptocurrency is a technological attempt to solve the problem of a fundamental lack of trust in our traditional institutions. After all, its powered by a set of de-centralized, trustless protocols. If you use crypto as an inflation hedge, that means you don't trust your government to not de-value your labor via printing tons of new currency. If you use it to carry out transactions, it means at least a small part of you has doubts that our that our current, centralized payment processing institutions won't unilaterally roll those transactions back or eliminate them outright in the future. Ditto for property rights and NFTs (and all the other use cases that guarantee a transaction is recorded by distributing it on chain).
Allowing crypto-currencies to supersede local currencies would not only put governments at the mercy of the mob (or perhaps a small number of whales and exchanges) for determining the value of their citizen's output, it would be an existential admission of their failure. Other than governments that have already failed at administering a currency like El Salvador, why would any self-respecting government with a functioning currency admit defeat like this?