It’s because every time the argentinian government needs to pay something, and don’t have the cash to do that, they print some billions and pay it. By literally printing monopoly money in huge quantity, they’re devaluing their currency every time they print a batch.

The rationale is that if they’re using the us dollar, the inflation will stop because it’s controlled externally

But by using the us dollar, every time the argentinian government needs to pay something and doesn’t have the cash to do that, need to borrow some heavy debt (at insane interest rate given their history where they didn’t repay previous debts)

And would need an huge quantity of them in a short time to exchange and dispose the pesos from people and banks

If it was as easy as “just don’t print monopoly money” they would have solved it.

Maybe it would be easier to just stop printing money than officially switching to a different currency