Why be an instructor?

I'm new to this forum, but I'm doing some research for another book I'm writing. So, here's my question:

For those of you who instruct other...

Source: http://www.motorsportforums.com/chit-chat/154349-why-instructor.html

Ivan Capelli Piero Carini Duane Carter Eugenio Castellotti Johnny Cecotto Andrea de Cesaris Francois Cevert