Having the big picture.
Tax rates, food stores, etc. are part of the big picture. Food rot isn't - it's on the order of a few percent. It shouldn't matter on the realm level. Let region lords and their stewards worry about it.
Also, I think you are still stuck in the ox cart system, mentally, where you would cart food around the realm for strategic reasons. Forget all about that.
Knowing who has lots of granaries and who doesn't isn't part of the big picture?
It's really really tedious having to do a census of the granaries, asking the region lords how many granaries they have in order to update the records. It's tedious, but I'll continue doing it.
I think any realm with a food deficit wants, in one way or another, for a central figure to be able to help coordinate the lords in order to minimize rot.
