Because for millenniums society had a gold standard on some level. Currently, the U.S. does not and most other nations do not either. Why would we revert to something that is held in extreme scarcity? Will we revert to slavery if we were to have a societal collapse? Absolutely not.
Hypothetical: It's 2021 and a massive earthquake has cause a massive tsunami that has ravaged most of the cities along the Pacific. Shortly after your nation is invaded and a war breaks out. No one has power, food, or water. After a long war with many lives lost and lots of destruction do you seriously think people would care about gold or try and use it as serious form of a new nation's currency?
> Will we revert to slavery if we were to have a societal collapse? Absolutely not.
Not sure why you're so certain about that - societies have abolished slavery only for it to come back in subsequent societies before.
Concrete example - India under the Maurya Empire, only for it to come back in medieval times.
> After a long war with many lives lost and lots of destruction do you seriously think people would care about gold or try and use it as serious form of a new nation's currency?
Yes, because it's happened again and again and again and again and again across countless apocalypses.
Hypothetical: It's 2021 and a massive earthquake has cause a massive tsunami that has ravaged most of the cities along the Pacific. Shortly after your nation is invaded and a war breaks out. No one has power, food, or water. After a long war with many lives lost and lots of destruction do you seriously think people would care about gold or try and use it as serious form of a new nation's currency?