Paper gold is a bet no different than a stock; it is a bet that the system and your counterparty will both be solvent when you need them.
a) It's a store of wealth. I don't expect to be able to go buy groceries with it, however I do expect to be able to cash it in for fiat post-depression if I need to.
b) I can move it abroad easily enough if I need to. I have immediate access to it.
c) It's cool.
It has also doubled in value since I bought it.
I am old enough to remeber the chaos in the silver market a few years ago, where it went to $50 per ounce and then crashed in two or three days. I'm not one of those morons.
It's fairly trivial to get lots of gold just above spot price. https://www.apmex.com/product/75/10-oz-gold-bar-brand-name
>And if you succeed, try selling it into the system again, without losing 30%.
In the scenario where the markets are collapsing and you need to sell gold for cash it's possible or even likely that it could be worth more than what you bought it for and even if not the discount rate you accept for selling it back may be worth it either way. If the market dropped 50-80% and you are only taking a 30% loss on gold that's clearly worth taking.
What this means is that, at moment in time, if the music stopped, someone would be left without gold - though with the distributed nature of everything, it’s hard to say who.
Fake bars are routinely discovered in storage, collateral, etc, see e.g. https://www.nasdaq.com/articles/chinas-kingold-shares-tank-o... for the most recent high profile (but by no means unique) example.