There's multiple factors at play, and the everybody-must-go-to-college bandwagon is certainly a big one.

I'd add a second one. It used to be the case that you could hire programmers without screening based on degrees. But that was back when programming was offputting and unappealing to anyone but nerds dedicated enough to become good at it.

Now STEM is hot in the collective conscious, programming is seen as a well paying job that's easier than becoming a doctor or lawyer, and corporate efforts are trying to recruit as many people into the candidate pool as possible.