Because they quality is so bad and the prices are so cheap. Having lived in these areas for most of my life I can tell you it's often only specific low quality

Because they quality is so bad and the prices are so cheap. Having lived in these areas for most of my life I can tell you it's often only specific low quality chains (Church's, Grannys, Jack in the Box etc...) or these "chicken wing/chinese food" shops that basically just fry up the worst meat and slather it in sugar sauce. I recall in high school, peers of mine would simply eat a bag of Doritos for lunch - as even the classes like Home-economics were largely just holding cells for teenagers until graduation.