My point is that it leads to some terrible gameplay:
People carelessly shooting into bunches of brawling mechs, to proooobably get that kill, hitting their teammates.
People getting in very very close to targets (much closer than rationally advisable) creating those close bunches in the first place (looking goofy btw...).
People intentionally blocking the line of fire of teammates, to be the one scoring that last hit.
People waiting for a target getting worn down to red-critical, so their own alpha will finish it (unbelievable, but some people actually do this).
People disconnecting mid-match, when they are damaged, but could still have made a difference, further hurting their team.
People being angry about "kill stealers", when they should be happy their team is winning.
And the list goes on, i guess...
I've always considered myself a team player. When i first started playing, my K/D was rather low. So i ignored it, still being happy as can be about every kill i scored. Still playing carefully and team oriented. But when i improved, and finally got past that magical 1.0 mark, i noticed myself starting to play cheesier, sometimes not telling my lancemates about a heavily injured enemy mech, as i think "hey, i got it in a sec..." And if something happens, and i don't get it, i have just hurt my team. So i force myself to always tell nowadays, however suspect that my lancemates don't always do it. There we are, even us, corrupted by our precious K/D rate...

Even if you know about it, and resist it, it eventually gets you (not everyone, i know, but some of us) and leads to cheesy play. What do you think about it?