Bulk buy, access and education are big factors.
If you only have £30 grand total, no wiggle room at all and need to feed a family of 4 with no car. You either need to sacrifice part of your £30 to transport or buy local in small more expensive shops.
If you only have £30 you can't buy the much cheaper per kilo big bag of rice and use it over 3 months, you have to buy the more expensive small bags of rice every week because you only have enough money to buy the exact amount of food and toiletries you will use that week.
If you don't know how to turn the random selection of yellow stickered reduced foods or even full priced but much cheaper seasonal produce into full meals you have to rely on ready meals or processed/packaged foods.
I did GCSEs in 2000, one of my subjects was food technology. We spent 2 years designing, branding, labelling and packaging a sandwich of our creation based on Moroccan cuisine. Completely useless in terms of teaching me to cook.
14 and under we made something every week but it was generally cakes, trifles, tarts, fruit pies. Whereas my mum who left school late 70s learned how to cook full meals, shepherds pie, lasagna and so on.