"There is no reason whatsoever why the same person should both create new knowledge and also teach calculus/cs 101/etc" How about that the person using the too

"There is no reason whatsoever why the same person should both create new knowledge and also teach calculus/cs 101/etc" How about that the person using the tool every day in the course of their work is probably going to be the person best placed to teach others how to use it? Obviously teaching is a skill and craft that has to be taught, but given two people of equal teaching ability, the person using the tool every day should be the better choice, surely?