Think of teaching as a way to constantly improve your skills as a public speaker and at the art of rhetoric. It’s a useful skill that will come in handy in many other areas of life. In addition, the quality of your lessons depends on your ability to talk in front of an audience, which is why you should never stop improving.
There is an enormous amount of literature and courses on the art of rhetoric and oratory. Though not required, it would be worthwhile for the instructor to study this subject in more detail if he felt he had certain challenges with it.