There are many reasons for silver supply deficits, but the same can be said for Gold IRA 401k investments. Yes, the myriad uses of silver are amazing, but the amount of silver required for almost all of them is tiny, so it doesn't have much effect on prices. Today's physical supplies meet demand, especially when recycling is taken into account. If there were a genuine shortage, you would know it quickly, and the same goes for Gold IRA 401k investments.
There isn't one, that's why the price is low.