We all know bitcoin runs in a decentralized system, so making it a legal tender simply means the government will also have control over it and it system which wasn't the original motive of it
Changing the previous system will be much more difficult and perhaps this is the reason why it is difficult for other countries to implement bitcoin as a legal transaction tool. Because having an official currency can conflict with regulations that will make bitcoin a transaction tool unless they make bitcoin an alternative.
So two colliding forces, which can't be met at all.
I know El Salvador has bitcoin as a legal tender, but can only be used as a means of payment and transaction which also works in other countries.
Even though they have established bitcoin as a legal means of payment and transactions, El Salvador still uses fiat currency as a means of transactions. But the advantage they have is that bitcoin is free to use to buy anything because bitcoin is legal as a transaction tool there.