I don't think it's about power. I feel more empowered as an engineer than I would as an engineering manager. As an engineer I have the power over all the intricate details of how systems work. As an engineering manager if I am lucky I would get to decide whom to fire if my team's budget gets a cut.

I think it's that there is only that much demand for solving really complex problems, and doing the same thing over and over is boring, so management is the only way forward for many people