Actually they are???
How come copper or lead or diamonds or corn or soy beans aren't a "storehouse" of value?
It wasn't all that long ago copper was used for making pennies, nickel for five cent pieces and silver for dimes. Actually, in case you didn't know, you can exchange one commodity for the other-- so if you're deserted somewhere in an strange land, don't be surprised if the locals don't recognise your "pile of gold" as wealth. As for food being a storehouse of value you'd have to think about its shelf life.
You're better off with metals ... oil and gas aren't too bad either.
FP........................................................