A country needs a stable currency in order to be able to establish a sound monetary policy. Unfortunately that's not the case with Bitcoin or any other crypto (except maybe stablecoins, but then they are tied to a different fiat currency or commodity). And of course most governments don't want people holding currencies that are completely out of their control.
that's it. after all, let's look at something simpler. bitcoin is not a stable coin so how can bitcoin stabilize an economy in a country that in fact bitcoin itself does not have a stable price and the fluctuations are very strong