Gold sort of works for sovereigns. It's crap for individuals. Any situation where you need to rely on physical gold is a situation where someone else will take it from you by force.
Fiat currency has become worthless many times in many countries without a total breakdown of civilization to the extent that gold no longer has any value (e.g., Argentina, Yugoslavia, Brazil, Weimar Germany, post-revolution France, ...)
I struggle to think of ones where physically-held gold is better than cash. It only happens when your government fails. In that case (e.g. a Communist revolution or civil war) it's easier to kill you and take everything than negotiate. Where it might have had value, e.g. an American holding pounds sterling during the American Revolution, the old money held value. Selling gold to paranoid individuals is so profitable for a reason.
(The only time it may be useful is if you can tell someone about to harm you that you can pay them with something offsite. At that point, however, wired dollars are an easier sell than waiting for a gold shipment that may or may not be accompanied by Marines.)
Gold is for when that stuff hits the fan: no one will take your paper money or if they do, you'll need 50lbs of trillion billion dollar bills to buy a loaf of bread. By noon the price will double.
If you're net liquid worth is well into millions, why not have a few hundred gold coins laying around? You might lose money (compared to the stock market returns) but so what. Peace of mind. Never know. All eggs in one basket and all.