There are lots of reasons, but here’s a highly significant — and counterintuitive — one from Marcus Buckingham’s First, Break All the Rules: What the World’s Greatest Managers Do Differently
Our research yielded many discoveries, but the most powerful was this: Talented employees need great managers.
The talented employee may join a company because of its charismatic leaders, its generous benefits, and its world-class training programs, but how long that employee stays and how productive he is while he is there is determined by his relationship with his immediate supervisor.