[IggleSniggle]

It got bootstrapped again because the government backing the currency fell, or the trustworthiness of the government fell.

Gold has a different "durability index" than "government coercion," but it's also not constant, and its rarity can be manipulated by anyone, whereas the rarity of a government backed currency can only be manipulated by the institution that backs its value in the first place.

I'm not making an argument that government backed currency is strictly "better" in all scenarios, only that it is not substantially "different" for most intents and purposes; ie it is not based on air, but a real-world quality: the coercive ability of an institution to maintain the value of the currency.