I would suggest that you've had experiences with bad middle managers. I say this all the time, but I only began to appreciate middle management when I became a front-line manager. An effective middle manager makes a whole boat full of people feel secure and strategically focused. They figure out how to leverage the strengths of their front-line managers and senior-level ICs, and how to fill in gaps. They know how to manage upward towards the executive layer, to acquire resources and summarize a great deal of complexity.