That would be a good idea as well, but as I said silver and gold bricks are not that portable. And if you are holding physical bullion, then the spread between buy and sell would be HUGE. If you are holding paper bullion, then there is no real point to it. Paper silver(futures, derivatives, etc. etc.) is pretty much the exact same as fiat currency, in the sense that their production can be controlled by a single entity.
While with bitcoin the spread is marginal and there is no "paper bitcoin". If you get what I mean, lol.