Gold has a lot of practical applications now (although is of course still treated as a ‘precious’ metal of value), but hundreds of years ago it was just a shiny metal. Why did it demand value, because of it’s rarity? Why not copper, because it was too easily found? What made it valuable ahead of other similar metals?
This is just speculation so not a real answer: many precious metals are easier to work than some of the harder counterparts like iron and steel. Secondarily, it’s harder to fake those. Even if you make an alloy counterfeit with the same weight when coated with the precious metal, you still need at least the previous metal and it would still fail other tests such as malleability.
Them being hard to fake is a really good point, good thinking.