Because of how stupid the overwhelming majority of them are.
I give it two years and if I'm not promoted, it's time for me to move on. And I give it two just because there's only 8 spots country wide in the position above me. If they can't see I'm head and shoulders above these buffoons in that amount of time, my faith in the company will have been lost.
Hopefully humility isn't an attribute needed for the promotion!