[nimble]

Given that we hammer it into every kid, who do you think these kids are who aren't going?

[EpicEng]

1. The lazy/unmotivated/really stupid

2. The smart ones who realize that they may be better suited to other tasks and don't feel like starting their adult lives in massive debt.

3. People who, for perhaps social reasons, exhibit very poor academic performance early in life.

4. People with random reasons for not going.

Anecdotal, but I sure know a lot of dumb, incompetent people with degrees.

[encoderer]

This. And not to mention, 4 year universities seriously under-sample students from poor, urban backgrounds.