Most academics looking for promotion are subject to publishing KPIs where publishing in various journals is weighted according to the prestige of the journal.

Most academics looking for promotion are subject to publishing KPIs where publishing in various journals is weighted according to the prestige of the journal. So you mandate a 30% discount on the KPI for any journal that isn't open access. Suddenly prestigious open access journals spring up and attract the best papers thereby getting more prestige points and so on. It's really that easy. Most academics I've noticed are more interested in their careers for which they're more than willing to exploit graduate students, holding them back a lot more than 3 years and so on to care which is why the problem continues to exist. Academics need to look firmly in the mirror when they ask why the journal publishing racket exists.