I propose that faculty compensation be linked to the earnings of the average graduate of their respective programs.
What makes you think they are not? How else could they hire anyone?
Average Faculty Salaries by Field and Rank at 4-Year Colleges and Universities, 2010-11
http://chronicle.com/article/Average-Faculty-Salaries-by/126586/
Nearly every Engineering Professor I saw in my college had first worked in his field. Nearly all of them were registered PEs.