>A professor involved in consulting etc. is normaly focused on this work. (For boring point of interest and $.$ ) The teaching is done by subordinates because the prof. is out of reach (and dealing with all those numb is such a waste of time). If all those involvment is over (aka "End of career") the remnant iiiis: teaching!
>
>Where are you getting this???

Physics? Experience? Common sense?
A professor hibernating on a sailing boat on Spitsbergen can not teach much. A professor sitting in each and every committee can not teach while sitting in the committtee. Do you realy think a prof with a advisor contract can work in the industry and the same time on the university? He delegates the most boring job to the gradutes and expresses that part of the graduates study is to learn teaching. For what I know more then half of the lectures is done by gradutes, iow inexperienced personal.

And the saying is from the academic circles, it is not my invention. I only explain it to you.