Sure, it may not be possible to stockpile every niche product, but this is literally food, perhaps the most obvious thing (up there with water and medical supplies) for governments to stockpile.

It's food for a specific niche though. More broadly, the US government does have a strategic grain reserve, holding wheat, corn, sorghum, and rice. Or at least, there was one, until 2008 when food prices spiked and the grains were all sold off. The reserve, called the Bill Emerson Humanitarian Trust, continues to exist to this day, but only holds cash/securities and no longer holds grains/commodities.

You mean the niche of babies?

Pretty much everything?

Lean does nothing but put cash in the pockets of those at the top at the expense of everyone else when there is a hiccup in the supply chain.

No, it makes the stuff cheaper.