I think it's multivariate. The rise of for-profit publishers certainly plays a large role, as does tenure track limitations, the booming business of education, and just the general pushback against openness. People fear the sunlight, no matter what "science" is supposed to be about.

I don't think it's any one thing or that there's an easy fix. For my part, I refuse to publish in non-OA journals and strongly prefer those who require/strongly encourage both open data and open peer review. PeerJ is one such journal which also features very fast time to first decision AND low fees. I cannot recommend them enough.