For poor people it is not just buying and getting the food home that is the problem. It is having the skills, knowledge and equipment to prepare it.
My mum is poor. She is 64 soon. Works in a NMW job. Can scarcely afford to buy food some weeks. Her element has broken in her oven. Will be £50 to repair. She broke the lid on her slow cooker. Couldn't afford a new one. She keeps her gas and electric costs as low as possible so doesn't like the stove on for hours on end.
She is lucky as she has 6 dcs and we all do bits and pieces of extra cooking for her to keep in her freezer.
My dsis is skint too. She works full time, has 2 dcs and a disabled dp. She is also pretty dyslexic and struggles to follow and read recipe books. She has a limited amount of healthy recipes she can do. Until I told her the sugar content of dolmio type jars she thought they were healthy. She can't afford to waste food so is understandably reluctant to try new foods incase she either ruins it or no one eats it.
By the time she gets in from work at 6pm the dcs have already had crap food like crisps, sweets or a bowl of cereal. Her DP can't cook due to his disability. She buys fruit which is always eaten and tries to buy healthier snack stuff. But she can get a bag of 15 packet of crisps for about £1.50. Or £1 for a pack of rice cakes. Or bread sticks. Or 1/3 of a block of cheese.
When you are poor there are a million and 1 reasons why you eat shit food. And a million and 1 people with an opinion on why you are fat and unhealthy (dsis isn't neither are her dcs but that's probably genetic as well).
But until you have made a choice between a food shop or gas and electric, when a 10p bag of crisps is a treat, when it's a choice between milk or bread, when you dread the dcs being ill because you can't afford to not work, when you don't have the bus fare to get to the doctors or even enough credit to ring for an appointment, then don't judge.
We would all like to get up in a morning and feed the kids porridge and eggs for breakfast. But when it's your disabled partner doing breakfast and you don't trust him to use the cooker and you are already 2 hours into a 12 hour shift cheerios might be the only option.
I have been poor. Bones of my arse poor. Luckily for me I had enough knowledge and kit to be able to knock up a veg soup. Or turn a tin of tomatoes into a pasta sauce. I could make 2 meals from 1lb of minced beef. And knew how to use veg and pulses to bulk out meat.
But not everyone has that knowledge. And as much as I find Jamie Oliver a twat his Ministry of Food book is really good at getting people who can't cook cooking.
Doesn't help if you don't have it tho. Or don't have a working cooker. Or can't get to decent supermarket. It's all very well saying takeaways cost more but they don't always. And a takeaway requires zero prep, zero equipment and zero gas or electricity.
Fruit and veg might be cheaper. Pulses might be healthier than meat. Homemade will always be better than processed stuff. Everyone, even poor folk knows this. Poor doesn't equal stupid. But poor does limit your choices. And not only are poor people skint they are often time poor as well. Or disabled. Or elderly.