Comment by LiquidSky

This is premised on promotions and other work rewards having any kind of rational basis or connection to the work.

It could simply be that spending time with your boss makes them know and like you more, and people tend to reward people they know and like, making up some post hoc rationalization about performance or whatever to justify it.

No one wants to think of themselves like this, though, so they would never admit, even to themselves, that this is what's going on, but I suspect for most people it's the actual reality.