Brink does reward for killing otherwise this game would not make a lot of sense to me.
It rewards less for killing, and more for team play.
"You get a little cookie for killing and a big cookie for doing an objective. Giving out the bonus for an Op taking a particular life (or disguise) is like putting frosting on the little cookie, sure it's still a little cookie but man does it taste good."
Nice description. But making that cookie taste that good would make most operatives go only for that cookie instead of hacking turrets or spotting mines, etc.