Ha, this was explored in some credible article here on HN some months ago, wasn't it? It made complete sense.

You can't be a nice balanced guy doing work which often dips in shady stuff, sometimes being responsible for killing innocents, or in extreme cases one's failed actions can send some region into death spiral of some small or larger conflict. No, you need (relatively) smart folks for whom emotions are just a tool to use on others to achieve your goals.

And this obviously has various side effects, some quite negative.