So, what about assists?
I play a lot of support in DotA2, where my KDR is supposed to be <1 (die instead of the carry, leave the kill to the carry), but I'm supposed to collect as many assists as possible, so that the team gets a benefit.
Similarly if you play as medic or engineer instead of sniper or heavy in any of those coop role-based shooters. In a team game, KDR of the team is what matters, and you have to work toward that as a goal. If you sacrifice yourself, so that your team can make two clean kills, then that's no good for your KDR, but the team gets a net gain.
Even in some arena shooters, KDR isn't important, because the only thing that matters is getting kills in, before someone else does. A 5:1 KDR is worthless, if someone else wont the match with 10:8 kills
A good KDR is NaN. Don't kill anyone, and don't die