We're still early. Gold and silver are well-known to many people who still know nothing about Bitcoin.
I'm no expert analyst, but it makes sense to me that the Bitcoiners are saving up first, then the rest of the world in the way they know, and they'll catch on later when they learn more.
It would be cool to be able to measure self-custody of these three (not that I think we should) and see how that adds up.
