Because that's mostly what they have access to, since sadly, garbage food is the cheapest food there is. Not only is healthy unprocessed food expensive, but it

Because that's mostly what they have access to, since sadly, garbage food is the cheapest food there is. Not only is healthy unprocessed food expensive, but it also hard to find in low income neighborhoods. But when it comes to school lunches specifically, they're getting those for free in many (most? all?) states if they're low income. So these changes should benefit them (even if the kids would prefer coke and fries).