If nobody cooks from scratch, who is buying all the raw ingredients at the stores? Every store sells them and I certainly see people buying them.
The Aldi's stores I go to ---one of which is in a extremely poor neighborhood, the other in a neighborhood with probably only $30,000/year household income-- are full of people, many of whom I would guess are poor and using foodstamps (which have been debit cards for years, now BTW), and who are buying raw ingredients. I see carts filled with flour, milk, eggs, rice, beans, pasta, potatoes, whole chickens, onions, bread, oranges, bananas, carrots, cabbages, broccoli, lettuce, peppers, apples, pears, kiwis, grapes, canned goods (does that qualify for raw ingredients?), pasta (qualify?), cheeses, yogurt. I see other things, too, including really bad stuff, but Aldi's sells tons of basics in these stores.
Foodstamps also can be used to buy seeds for food plants and Aldi's sells these in spring.
My poor neighbor has been asking me over and over to please drive her to the park where the police stables are to get some manure for her vegetable garden. (Haven't been able to work out the day & car use yet.) She eats very inexpensively and deliciously and grows enough to share with me. I give her things from my garden; she gives me things from hers. She does eat a lot of carbs, especially rice, lentils, carrots, and homemade bread, but I believe that is how she ate even before she was poor. Oh, she does use a lot of oil in some dishes, a liquid oil of some sort, not sure what. She eats a little meat, but not at every meal and usually only bits of it in a dish, I would say easily less than 2 ounces per serving, probably less. Yeah, she is fat, but not lazy at all, and I would say well nourished, just over-caloried. I don't think she knows anything about nutrition, but I think she does well anyway.
So enough of my pointing out that 1) not all poor people eat crap yet indulge in luxury foods with foodstamps, and 2) some people still do cook from scratch. "You" aren't the only one.