Maybe because they aren't that many ways to teach? there are certainly some known fundamentals and maybe some tricks that improve teaching marginally, but I dou

Maybe because they aren't that many ways to teach? there are certainly some known fundamentals and maybe some tricks that improve teaching marginally, but I doubt there is some pedagogical silver bullet waiting to be found. But more importantly, professors would do a better job if they had incentives to teach. It is time consuming to prepare a class, especially if there are labs to set up and maintain. Even worse, some professors have to teach classes for things that are not their domain of expertise. In some universities, it's not uncommon that, let say, a professor specializing in logic has to teach operating systems. All the time spent on teaching is basically lost as career advancements are based on research and administrative work.