The thing is, rating is acquired by teamplay. Killing the enemy, healing and resupplying teammates, building and destroying things, all helps your team and all contributes to rating. I've seen team-playing engineers acquire higher ppm than straight fraggers. Still there is a margin where focus on the objective itself is ignored, and even on some occasion they try to prevent their teammates from getting the obj so that the map can continue because they are doing good on that map.

On all servers I play on, no one plays for rate, everyone (myself included) play only for fun and obj. Most raters play on servers like FA, so just find another server if you don't like how some raters play.