One: gold is the og currency, it doesn't have to prove its value because it already did. Two: it is also being actively used for transactions, look no further than jewelry. If you have gold, you will find someone who is willing to exchange it for something else with material value in any city on the planet. This is not the case for crypto.
No? You don't think the following statement is as true as the one you made?
"If you have Bitcoin, you will find someone who is willing to exchange it for something else with material value in any city on the planet"
My experience would tell me otherwise, but maybe I'm a outlier.
1: Cryptocurrencies can still operate over distributed mesh networks or sneaker-nets in a semi-doomsday scenario.
2: With gold, it is difficult to verify its authenticity vs some impostor alloy without the necessary tech/knowledge.
Edit: the bottom line is that in a doomsday scenario, people have little use for bitcoins or shiny yellow rocks.
Bitcoin wins.
See, we can do this all day. There are points of comparison and points of departure.
However, gold has a fundamentally stronger argument for its value. Gold is useful: it has unique physical and chemical properties.
Gold is drastically more difficult to transact in than bitcoin or any cryptocurrency. Not only is it extremely difficult to create exact change to pay in gold (shaving of milligrams per dollar?) but there is zero infrastructure or education on how to verify that the gold is real. Even modern nation state banks have been fooled by tungsten cored bars of gold.
There are plenty of well established crypto apps that make receipt, verification, and conversion into your preferred cryptocurrencies or fiat currencies instant and effortless.