I have spent more than the last 40 years visiting Japan every year; usually for more than a month. From the beginning in 1971 I have observed that a typical Japanese family meal is created by bringing home from the grocery about 90% of the food to be served which has already been prepared and adding roughly 10% of something prepared in the kitchen by heating (and that includes tea and soup).
That seems to me to be the standard in Japanese families and home eating environments. It includes families with children.
This has never been the practice in the United States. Up until the 1980s nearly all families prepared nearly all of their own home meals. Some of it was bought prepared such as dessert and occasionally pizza. Many subcomponents of the meal were bought prepared such as sauces and drinks.
Since the 1980s there has been a slow movement from the American household style of dining to the Japanese-style.
Supermarkets, fast food retailers and places like Costco now provide a wide selection of prepared food for the American home pallet.
We are going Japanese. I think it's because the quality of the food is better for most people when it is prepared by commercial kitchens. (Though 'foodies' will deny it.) I also think we find food preparation to be less of a family responsibility and more of an occasional recreational activity.