[tftfmacedo]

You should try living a country with high inflation. People lookup exchange rates every single day.

[ars]

And those people do not willingly use that currency - they are forced to by their government.

Whatever currency it is that they are comparing to is the currency they really want to use, and probably do on the black market. I'm also confident that that is the currency they keep (or try to keep) their savings in.

[ohashi]

And you see real currencies being used in many of them as black market currencies instead of the national currency. You can also see countries trying to stop inflation by indexing to other, stable, currencies.