1. Ants, cockroaches, and flies invade one's apartment fairly regularly, and will stay if you leave food for them.
2. Inconvenience of going to a grocery store every day.
3. Unavailability of non-basic ingredients within a short distance of one's home. I can walk to a nearby store to get some carrots or cabbage, but if I want bitter melons, black radishes, or oyster mushrooms, I have to drive to a different neighborhood. And once at a store there, may as well load up and buy in bulk to reduce the number of trips.
3a. Unavailability of affordable ingredients within a short distance. Buying in bulk at a big store gets very tempting when one notices how much cheaper it is per pound. (Alas, one forgets that some of those bulk pounds will wilt.)
4. Unpredictability of consumption. Maybe the toddler really doesn't want tomatoes on the table today. Maybe there is a production outage at work, so you don't have time to cook.