Academic for professional disciplines

Many academic domains for professional disciplines, think of law, architect, psychology, performing arts, engineering, are allowed/expected to practice their profession besides teaching that profession. One exception is teachers and educational leaders: those teach teachers might have taught in schools before, but once they take up academic positions, often no longer continue their school-teaching practice. It is often the same with educational leaders: they might be school leaders before, but once they take up academic position in educational leadership, few (if any) retain their school leader position. The best scenario is to become some kind of a consultant (though still removed from day-to-day operations). This raises the question of why (other professions tend to be project based while teaching often not??) and how much might have been lost in this potential distance/disjunction.