A large group of kids learn to pass the test and move on. There's very little unstructured exploration or debate, on the whole. I had some excellent teachers and classes in high school, and I had some awful ones, but I damn sure never had freedom to mentally explore interesting topics in-class. High school was a means to an end; just a way to leave home and go to college. Personally I didn't take that approach but I know a lot of people who did.
At that point, a student's approach is "do academia to get to next stage". It doesn't make you care at all about Shakespeare.
And for families that are monetarily burdened by college (read: every family, save a handful), you're not going to go waste $40k/year for something with no prospects.