Overreliance on slides has contributed to the absurd belief that expecting and requiring students to read books, attend classes, take notes and do homework is unreasonable.
Courses designed around slides therefore propagate the myth that students can become skilled and knowledgeable without working through dozens of books, hundreds of articles and thousands of problems.
If slide shows are so bad, why are they so popular?
Universities measure student satisfaction but they do not measure learning. Since organisations focus on what they measure and students like PowerPoint, it stays, regardless of its educational effectiveness.
On the other hand, when I see something pervasive that exists counter to my own values, I wonder (a) are my values out of step and (b) what are the incentives? I think more research is needed.