For perspective: I come from a country where "cafeteria" food at school is good and affordable (most is less than the equivalent of 5-10 USD max and it's not slop, it's actual food), but it's not an obligation for everyone since it's up to the student if they want to buy something or bring their own lunch.
The "cafeteria" in my school isn't a typical American one, rather it's closer to a canteen where they sell food you can purchase from cup noodles, fried stuff, sandwiches, baked goods, etc. also appliances like a kettle or microwave are available in the dining hall for students to heat up left overs if they wanted.
The thing I tend to notice from American schools (according to US movies, there's bias whether it's true or false) is that they tend to depict kids always heading for the cafeteria for recess or lunch picking up whats available instead of bringing their own food from home (left overs from dinner), why is that the case?
My kid just started TK and the school is serving such a high poverty area that they give free breakfast and lunch. It's hard to pass up, and isn't the worst quality in the world but still a little more sugar than I'd prefer. Fruit yes, vegetable no, and loads of dairy (which is a thing thanks to US subsidizing farms, this is where that surplus goes. Corn syrup, too though, unfortunately).
It's also kind of a lot of trouble for two working parents to prep a lunch for multiple kids every day. Leftovers are great, but they don't always hold for the few hours they're in a bag. I'm allowed to bring food to them at 11:30am, but I'm working so it's a non starter. My daughter also attends a Japanese Saturday school though and prepping a bento box is required.