No argument from me. My point is that I suspect the busiest units which run out of stock start the day with exactly the same stock levels as those which historically sell less. They can't transfer stuff between units through the crowd so miss sales where their records should be telling them...
Less mediocracy than practicality. No point in buying stock you will just throw away so perishables need careful control.
That doesn't mean that perishable stock can't be replaced with something with a longer shelf life (bottled beer for example). Nor does it excuse the caterers' apparent...