@LukeAlmighty if I had to guess it's probably because we naturally like to horde and obtain items of great value because that's how you get a mate.

And because we enjoy gathering materials similar to like a penguin, you combine the two together and whenever we determine something is valuable or an item of high value we like it a lot.

It probably doesn't matter what it is but it just needs to meet those general criteria everything else is nuanced.