There are few people that I know who cook. Most of them are older, but not all. If you go out, you don't have to clean your kitchen afterwards. Working mothers are challenged to work all day, deal with the family in the evening and cook on top of that. I have usually cooked foods that gave us more than one meal, such as pots of soup, lasagna, casseroles. I often divvied it up into containers and put meals in the freezer for later.
There are many foods from the grocery store that require little or no cooking and don't leave your kitchen a mess, but they don't store well for long term, without a freezer. The freezer sections and the delicatessen sections of grocery stores have grown over the years.