You're saying companies exist to make money but an isolated factoid like that doesn't make for a productive discussion. Lean manufacturing may be good for individual corporations but it's clearly bad for society and society needs to continue existing for corporations to exist.
Tying up $ in assets that are sitting in warehouses instead of using that $ elsewhere is a not benefit to society. One premise of lean is to match variation in demand to supply as quickly as possible, you should be calling for capacity to scale production and lower lead time, not hold inventory. You might not even hold the right inventory.
> Tying up $ in assets that are sitting in warehouses instead of using that $ elsewhere is a not benefit to society
As we can clearly see now.
> One premise of lean is to match variation in demand to supply as quickly as possible
This is done at a cost of making the whole system less resilient against demand spikes and in-chain disruptions. A perfectly lean system would be following predicted demand precisely, maximizing efficiency at each stage, and as a result break down as soon as anything in the chain changes by even most tiny amount.
I'm a layman in supply chain space, but my observation is that the risk horizons on the market are too small - anything that happens less frequently than once every few quarters may as well not exist. So throw in a big enough wrench, and everything is in shambles for way longer than the existence of initial cause (see the so-called "bullwhip effect", or as it's known in control theory, a positive feedback loop making the system oscillating and unstable). It could've been helped if there was enough buffer in the system to allow time for expanding manufacturing capacity.
As for what to do with different kinds of inventory, two observation. One, the earlier you are in the manufacturing process, the more potential buyers for your product you'll have - so it's that less risky to keep inventory. It's probably not worth it to stock too much of front left doors to 2020 BMWs, but a sheet metal wholesaler doesn't have to run lean and choke everyone downstream when the foundries or miners get disrupted by an epidemic. Two, for some stuff it's really the role of the government to keep buffers. PPE and food would be this. Imagine if any of the Western countries actually had a proper (Cold War style) stock of PPE for a pandemic, and food for everyone for a year. There wouldn't be any worry about staple shortages or hemorrhaging medical staff. There wouldn't be a problem with PPE manufacturers expanding capacity either, as the government could just buy enough goods to fill in the entire buffer capacity they plan on depleting - which would give the manufacturers a chance to recoup their investment in meeting a temporary demand surge.
Bottomline: not saying that fat is good, but I think there's such a thing as being too lean, and that is the problem we're having.
Potentially the same problem, except you shift it forward in time. So perhaps the factory staff can recover and get back to work before the buffer runs out. Or competitors can ramp up production in time to compensate. Point is, a buffer is adding inertia into the system, an integrating block, which is often a good thing, as it eats oscillations. It's essentially the same reason you put capacitors next to the power supply in electronics - they eat voltage spikes, preventing your device from shutting off just because it briefly drew more power.
