One valid point is that many types of exchanges are ultimately based on some form of legal tender currency. Foreign money many be good for awhile, look at how many countries fall back to U.S. currency when their money inflates off the charts. However, if our currency takes a dive or gets cancelled, a lot of countries are going down with it.
A trail goes two ways and looks different in each direction - There is no such thing as a timid woodland creature - Whatever does not kill you leaves you a survivor - Jesus is NOT a bad word - MSB