Earlier quoted context omitted.
If you live in a city, you typically go to a supermarket 3-5 times a week. And if your family is small enough to fit in a normal car, you can easily carry the groceries. Those trips don't take too much time either, because urban supermarkets are smaller than suburban hypermarkets and designed for quick visits.
That's a lot more time and effort than should be necessary. You should have at least a week of food just to prepare for an emergency.
Going to a grocery store a few times a week is not a lot of effort. Urban grocery stores are nearby, they are optimized for quick visits, and you can often buy groceries when returning from somewhere else.
You should have emergency food at home, but many kinds of fresh foods are best eaten within a day or two. If you only go to a grocery store once a week, the quality of the food you eat is worse.