One thing I've never understood about this position--why is university such a stark cutoff? Most everyone agrees students shouldn't have to pay for their books

One thing I've never understood about this position--why is university such a stark cutoff? Most everyone agrees students shouldn't have to pay for their books in K-12. We agree it's better for our society if primary and second education is not gated by a family's wealth. Not just ethnically, I think it's better for a nation's economic productivity. The whole world is getting more educated, and it does feel like a bachelors or equivalent training is what a high school diploma was 60 years ago.