They don't produce anything, at best they're taste arbiters and at worst parasitic middle men that happen to control the budget; funny how that always means they get more of it.
The best long term performing companies are run by technical people that happen to be competent managers. As soon as the professional managerial class takes over they quickly figure out their most profitable move is to cheapen out on engineering and trade in the future for bonuses right now; they'll be long gone when the company craters.