Thing is, Kai, a lot of Lords don't want to pay any attention to the state of their region.
If the game sent them a message every day telling them how much food they should buy for their region that day, they'd probably ignore it.
Having a person do it for them? That gets them to do it.
Well, some of them. Others just bitch and moan about their Lordly sovereignty and still won't sell or buy food.