It's less about ego, and more that the removal of ambiguity in the workplace hierarchy is itself a social attack. If Alice is considered "better" than Bob, then Bob cannot act as if he were "better" without getting smacked down for being uppity or putting on airs or the like.

It's not about the money. It's not even the fact that you ranked them. It's that you ranked them publicly, and from a place of authority to boot. And worse still, on a one-dimensional scale.