Just an idea off the top of my head, the entire concept of KDA is obviously meaningless and has nothing to do with winning the game (it is not, as many think, first to 50), and only used as fuel to troll your own teammates. Players aren't ranked by performance at the end of the game by points, which would be needed. Titanfall uses that kind of system, and ranks players at the end of matches by not just k/d, but also how many minions you killed (which are worth way more than enough to offset one's k/d) or objectives you captured.
For whatever reason, Dominion has the way-more-advanced points system that includes that, objectives, just other stuff to add into a points score. Ascension followed the same mechanic, and it was good.
Other games use a similar system, a la Battlefield (or the aforementioned FPS-MOBA-hybrid 6v6 Titanfall, in which case you can have the highest score if you kill all the "creeps" and only passively target pilots/titans, if you ever kill any at all and just go minion-hunting), in which KDA means nothing because by itself it doesn't win the game, and it's thrown in everyone's faces that there's more you need to think about. People are graded on their points score, very similar to Dominion's way of doing things.
Why we haven't adopted that is staggering. KDA is an idiotic statistic that means nothing and never has meant anything. If anything, only the "D" in that matters, because that means you're feeding if it's relatively higher than the rest of your team.