Literally not being at home to eat home made food is obviously a case where other factors dominate.

However, I really don't think that's the general case people are thinking of when trying to argue that it makes some kind of economic sense for people to eat a fast food diet. The average person does go home at some point, especially so for families.

Or more specifically, it's the claim "I can't go to the grocery store and make this meal for less than a fast food meal", that is absurd.