Probably because a lot of smart people find doing other things less managerial more rewarding.
Every time I have to fill a spreadsheet that could be generated by a computer program, I die a little.
Or, as pg could put it, sometimes a promotion into management resembles being scheduled for daily waterboarding sessions. Being dragged into a cargo cult is no fun.
If the suits are so incompetent, why are they in charge of everything? Perhaps they aren't optimizing for what you think they're optimizing?