I think there are a number of other base metals/products that one can invest in to store wealth
The problem is wealth density.
$40k gold is the size of a smart phone.
$40k copper is 6.7 tonnes
Reassure me, you don't know anyone with 6.7 tons of copper in his house, do you? Even the Gypsys don't have.
Thats exactly why copper is not used as a store of value: storing big wealth with copper would be impracticable from a physical point of view. And if you think storing is a problem, try moving that wealth.
So wealth density is a very important quality for store of value. Gold is good, diamonds are better, but bitcoin is simply unbeatable from this point of view.