Argentina is the classic case of a country that does not trust its own currency. Traditionally, Argentina suffers from inflation, so the US dollar is the refuge for most people. Actually, during the decade of 1990, Argentine currency was fixed to the dollar. So, during that time, Argentinians actually used their currency or dollars.
I still remember those years when Argentinians who traveled outside their country were surprised that in other countries did not accept their currency with the exchange 1 to 1 towards the dollar. They were offered far less than that.
Obviously, that fixed exchange was impossible to sustain, and ended in the crisis of 2001.
In fact, nowadays, there are four times more dollars (link in Spanish) in Argentina's economy than its own currency (pesos). The amount of dollars per capita in Argentina is the highest in the world outside the USA. The exchange is fixed by the government, but in the black market you can buy dollars (called blue dollars) by paying double. In fact, newspapers show both exchanges (check upper left corner).
So, even though Argentina still has its own currency, their own people try to not use it and buy dollars instead. But, since dollars are scarce in an economy where everyone wants dollars, the government sets a limit of dollars that each person can buy (200).