Yeah but it's more about "time" and money than availability.
People don't have time to cook a proper meal due to work, eating healthy is also WAY more expensive than just eating whatever fills you the most.
Translated to kids, well there's just enough time to get them dressed and run off to school, hope they pick what's good for them and not something that they like with whatever little money they are given.

That aside, I could somewhat trust meals on private schools to be decent or to not get the kids sick... Not as much, at least. Now public schools... I fear for the poor kids as I expect these meals to become someone's nepotism and not care at all about it being healthy, undercooked or expired.