Example: Guy1 fights against an enemy1 for an amount of time, hits him a few times and hurts him severly (10% hp left). Guy2 jumps in from the back, hits enemy1 and kills him. Why should Guy2 get many points for this? All the work was done by Guy1.
Watching some of the top scores over time you'll notice thats exactly what they do. Let the battle run for a while and come to the battle when all enemies are hurt by the teammates that hit them in first place to get easy kills.
As others mentioned, if guy1 lost because guy2 didn't help, and then the enemy1 went on a rampage, it could cost the team a win. Finishing people off is important, kills from behind are important too, cuz it's really hard to kill top players from the front.
If guy1 had the enemy1 down to 10%, he would have already picked up 5-7 points during the fight. One of the glitches right now is that a finishing blow seems to be calculated on raw damage, it's not capped by the target's actual HP, so guy2 would get like 5 points for landing a big blow, when he really should just be getting 1-2 points for finishing the remaining HP, and then maybe another 1-2 points for a kill bonus (This is why lancers get so many points still, cuz they get massive scores for doing a 150hp damage couch attack on an archer). So guy1 picks up 5-7 for doing the hard work, and guy2 picks up 2-4 points for the important kill blow.
