Why would governments use a blockchain to enact fiat? Why would they just not print it at random as they have always done? It is easier, they know how that system works, and there is no advantage to them to put it on a blockchain.
Blockchain advantages in cost reduction
There is absolutely no scenario under which a centralized blockchain implementation can be a cost reduction over a database.
I was not comparing to database. I was comparing to fiat (minting, transporting, securing, coins and banknotes; protection of databases via redundancy, physical protection, use of expensive closed-source software and devices...)