I'm not sure why learning how to teach effectively isn't high on the list of objectives. Its all the college PR campaigns spit out along with research, but the latter is all that matters. My wife was a 21 year old grad student and handed a large class of Sophomores and Juniors to teach a 200 level course. She had one-semester under her belt as a TA prior, but no formal training on how to teach, etc.
I have professors who ramble on during examples of the most mundane things simply throwing more and more effort into a failing effort. And there are the complete opposites who never cover the material clearly and never ask students if they understand.