Well, if the Lean methodology is so great for the entire supply chain, why it suddenly shouldn't be applied to the last link - the consumer? Building up a buffer is against just-in-time principle :P.

(The truth is, JIT supply chains simply aren't designed to survive events like a global pandemic. They're control systems overtuned to extract the last bits of efficiency from trade, and fall into bad oscillations when disruptions happen. As we can see today.)