A matter of perspective ...
Having grown up dirt poor after the WWII victory years, I can say that one needs to live in the US environment to really understand the problem with poor families and their diet.
First off, there's really no food education in US schools; nothing much about basic cooking or nutrition. In my day, there was some "home extension" material pushed by the government, and Home Economics classes for girls, and Shop classes for boys. All home skills were assumed to be taught by mothers and grandmothers. Poor diet habits got passed down the generations. Over time, that has devolved into a gross divide between "fashionable" food habits in wealthy areas, and prepared fast food habits for poor inner-city or rural districts. And basic living skills are no longer part of the curriculum in public schools.
More recently, access to wholesome, affordable food has become problematic. America's tumble into corporatism is reflected in the megastores and where they're located; usually in upscale, wealthier areas. The concept of "food desert" is a uniquely American development. Poor neighborhoods are left with rip-off corner convenience stores, and junk food outlets. And if there is access to a proper supermarket, 95% of the shelf space is dedicated to over-processed quick 'n easy stuff, and acres and acres of rumbling freezers filled with ready-to-eat convenience stuff. Basic foods are on the floor shelves, mostly out of sight, and wholesome produce -- veg and fruit -- is sorted, waxed, and polished, and is obscenely expensive.
Two other factors have a profound effect. Lack of cooking skills, and lack of a proper kitchen and cookware to prepare nutritious meals. It takes both taste acculturation, cooking education, and accessible (and affordable) cookware to prepare family meals, day after day. (Decent cookware has become absurdly expensive in recent years; that's why the typical donation-based Thrift store shelves are usually stripped clean of any good skillets, pots, or pans.)
Give a poor or homeless US family bags of rice and dried beans, a sack of spuds, a head of cabbage and a bunch of carrots, and you might as well go ahead and kick them in the teeth for good measure. Most are not able or equipped to handle food in that form. A box of quick ramen, a pack of instant mac n' cheese food, or a Big Mac with a super-sized side of fries is far more accessible to them.