Earlier quoted context omitted.
When you're facing starvation, such modern niceties will go out the window.
That logic is good when the farm is next door and you can pay cash $ for a bushel of feed grade corn or whatever. But it starts to fall short when you're still relying on the normal supply chain to get food in a city center. Desperate and hungry people will be resourceful, but it likely won't be as simple as a lower grade of corn in the produce section of the grocery store.
Failing to do so would take a huge number of people whose job description is to do exactly that. If one tries something new that works the rest is sure to follow.
They are puzzling all the time, how much eggs to buy? how much potatoes? how much this? how much that? They never get it exactly right, they are always a few bags of apples short or have to throw them out.