I worked at a food store as a student a long time ago. Remarkably few customers are weekly. We did sell entire cartloads of food on certain days at certain times but it's pretty rare. Most of the people walking in will have to skip a meal that day if they did not stop at the store for just one thing. Then add some impulse purchases. Most people walk out with one grocery bag, some walk out with only one item. Where I lived, most of this behavior was poor planning not financial. Most of the items were pretty nice, not the cheapest. People who can't plan ahead to have enough eggs or whatever will never plan ahead enough for the enormous latency of very slow delivery. Those eggs they're buying, will be cooking mere minutes after purchase not hours.