Cooking takes time and effort, which many people lack. You need to make an initial investment in utensils and appliances, which poor people can't always afford. And if you don't already know how to cook, learning it on your own can be risky. If you make a mistake, you may end up losing the food, which poor people again may not be able to afford. And learning it takes time and effort anyway.
In many cultures, men traditionally didn't know how to cook. It was not their job. That wasn't a problem, as long as men lived with their parents or in an institutional setting, until they got married. But in a modern, more individualist culture, such attitudes are holding men back.