Regarding the "skilled" vs "unskilled"-- no one is saying people in those types of jobs don't have any skills or talents. These are recognized terms for certain types of jobs, like "trade", "profession", "blue/white collar", etc. Not a reflection of the value of the people working those positions.
Transportation is a major factor for the poor. Since it's expensive and inconvenient to get a taxi or ask someone to drive you to the grocery store, some may only shop once a month or less so the easiest items to buy are cheap processed foods that will last a long time. It's also challenging and time consuming to meal plan out that far, so midway through the month you may find yourself with just random cans and items that you can't pull together a healthy complete meal from.
If you can't get to the grocery store easily it doesn't matter if you can buy the supplies to make a cheaper, healthier meal.
Transportation is a major factor for the poor. Since it's expensive and inconvenient to get a taxi or ask someone to drive you to the grocery store, some may only shop once a month or less so the easiest items to buy are cheap processed foods that will last a long time. It's also challenging and time consuming to meal plan out that far, so midway through the month you may find yourself with just random cans and items that you can't pull together a healthy complete meal from.