It's deeper than that. What matters in management ranks is subservience. A bad manager is someone who is not subservient or exhibits individualistic behavior. Direct reports leaving has no bearing on this at all, so it doesn't matter. in fact companies predict how long rank and file employees will stay on average for a number of reasons such as estimating recruiting expenses. I think what Bezos meant was that rank and file are not of the power structure, would never be able to influence the power structure, and are expected to leave after a time. The power structure would be protected at all costs even if every last non-administrative employee was driven out.