The trite saying "a good diver is always learning" really applies here. I know many instructors that may teach openwater only students, but go on to many other styles/types of diving. Those other types of diving are the instructors way of gaining proficiency, skill, and knowledge outside the realm of their instructor roles. I had a Openwater I and II instructor who strongly advocated cave diving as a way to improve skill level, even though he refused to be certified as a cave instructor.