One reason why it's so easy to sell, is that college is a near universal experience for the middle and upper classes, and being an expensive experience, people credit it with much of the personal growth that happens in one's early 20s. They also credit it with making them good at their field.
"I really learned how to think in college"
"I really learned how to be apply myself in college"
"I really learned computer science in college, which wouldn't have happened if I went via some other path.
etc.
It's far too painful for most people to think "I could have been an equally skilled person if I'd spent that time doing something else".
I come from a long line of people who've succeeded without going to college. When I tell people I've known for a while that I dropped out of a community college they usually seem stunned and surprised that someone could actually have a reasonably intelligent conversation with them (and be a decent engineer) without that history.
My experience is that you can read books on the humanities, and CS, and get work done AND not kill yourself in the process. Maybe the road is a little longer in some ways, but you also come out of it without debt, and you get the benefit of having a very different set of formative experiences than your peers.