This is and is not true. The implicit value of a currency is backed by being able to tax the citizens. This is why there are federal but not state / province level currencies as the friction of conversion is a dead weight loss.
Elaborate? Not sure why this would be true.
I'm pretty sure there are plenty of "commodity currencies" (shells, salt, even gold) that achieved value without some central agency controlling the currency that could also levy taxes.
You make a valid point, I do trust that our government will come to collect what's due from the citizens, but what about the corporations?
Worth noting there are quite a number of what are known as Community currencies still active in the US & Canada:
USA: https://en.m.wikipedia.org/wiki/List_of_community_currencies...
Canada: https://en.m.wikipedia.org/wiki/List_of_community_currencies...