Getting randomly attack while trying to play - the other teams killers are preventing you from achieving anything.
Runners - semi-naked players that are good at manual block or have a shield to avoid losing the ball, also serve as catchers if the other team has a ball
Killers- murder everyone indiscriminately, stops other team from getting organized.
Rounders- do what needs to be done.
Catchers- fast enough to catch the other teams runners, or good with a ranged weapon.
Note that the goalie should have a shield so archers can't just pick them off or flinch lock.
Seriousness: Killing people is a very effective way of winning. Why compete with the other team when you can force them to spawn farther away. Even a single person you know is going to stomp everyone else in straight up fights ruins the balance, eh hrm I mean works the best for their team.
Bring stones to throw at people.
Edit: I think it's called Rageball since you rage at the other players stopping you from what your doing and murder everyone.