R.P. Blackmur, a Princeton Professor of English, dropped out after High School. Kenneth Burke, an important writer in many fields and a visiting professor all over the place, never got his B.A. A grad school friend had a brother working on a Ph.D. in sociology at Chicago. He had to get that degree because he didn't even have an elementary school certificate. An important professor of classics at the U of Mich got promoted to full professor early because he had no Ph.D. and the department head, about to retire, thought some asshole succeeding him might fuss about that.
I don't know if such things happen any more or not. They were rare in the past.
Carrol