PhD students are not trained to be good teachers!

Even in top research schools professors spend a considerable portion of their working time teaching classes. Yet, from what I know, PhD programs typically do not require their students to take any courses on pedagogy. This seems to be a bit strange. But we all know why, right? Nobody cares about teaching in research schools - it's all about publishing. But students are paying big bucks for tuition. Don't they deserve to be taught by people who are well-trained on how to teach?