It's not so much as petty as it is a need to control the direction of the conversation. By placing a stake in the ground, the conversation will stay in the general area that the company (and I'm not including only Apple here) wants it to. Part of the field called "public relations".

A lot of people about the top care more about their position and the power it represents rather than what it actually means for the company. Yeah, they are egomaniac children, most of the time.

I actually see this rather as evidence of a strong corporate culture which recognizes the need for execs to take responsibility for mistakes, as the chapter from the Lashinsky book on Apple management famously quoted about the rubric being crossed when VP's are promoted: http://www.businessinsider.com/steve-jobs-on-the-difference-...

(Kinda wish a few more companies made this expectation clear... too much deadwood at the VP level in many IT companies I deal with...)

the game to get into that seat is not exactly set in favor of the magnanimous nice guys.

It's not really that petty. This stuff is the essence about what leadership teams tend to deal with.

Not just executives, a majority of non-leaf nodes (but not all). The more money that's at stake, the more petty and childish people act. Acting like a child is an actual strategy people use. If people act rationally it provides a stronger basis for criticism and makes them a target. If someone acts like a child then people say "wow that person's a real stupid jackass that only wants power." If someone tries to rationalize bumping off their competition, its "wow that person is a real threat."