Ketchup vegetable wasn't "education"; it was political football with school lunch funding and minimum vegetable requirements and trying to feed kids when they'd simply throw away any salad they were served.
But I'm sure the reason kids threw away fruits and vegetables because they were terrible; not necessarily because they were healthy. I don't know if it's a low value put on food or cost-cutting...I'm sure both are related. You can see this in places other than schools, outside of every corporate meeting is a tray of terrible honeydew and cantaloupe. Most lettuce and tomato don't really have flavor but seem to leach off-flavors. In my personal experience, when I find out someone says they don't like a certain food about half the time it's because they've never had a good example of it.
It's difficult because fresh food spoils so much more quickly than other, cheaper, and less healthy foods. But what's crazy is that today we have way better technology than most of human history to make even the foods most prone to spoilage cheaper an accessible...it's just relative to frozen pizza and ketchup it's more expensive.