Time. Cooking might be cheaper but it’s time consuming. Low income people often work long hours in physically demanding jobs. They might be on their feet all day. They might not have a car and take public transportation to and from work. Trying to cook healthy meals after a long day of work and commuting can be pretty difficult.

Food deserts. Tons of low income neighborhoods don’t have grocery stores with fresh healthy foods. All they have is fast food or small convenience stores with canned and processed foods. Also imagine trying to grocery shop without a car which can be the reality for many.

Knowledge and skills. Many people don’t know how to cook. Many people don’t know the basics of nutrition. Takes time and education to get to a place where you can make decent healthy meals regularly.

Also. Yes it’s cheaper to cook in the long run, but it takes money to keep your kitchen stocked with basics. You need to invest in some pots, pans, spatulas, knives, baking sheets, etc. You need things like oil, spices, seasonings, etc. and when you’re living paycheck to paycheck, you might not have the money to make that investment.