First I would like to assert that I am a little rusty on pirates. I have scored in the 40K-45K on occasions. Usually it is with 4 on 4 and the team members on both sides are not very good or not aware that they should not pick up health if they are losing badly.
Occasionally you get someone that is determined they can kill you even though they are losing so they keep recharging. I would theorize under the exact right conditions it would not be because of "cheating" if the other players just won't die and it is not a "canned" game.
With that said people can run up the score with a version of what some have called "sitting ducks" where one team voluntarily losses badly instead of just losing they continue to get health so the other team continues to get points.
Generally speaking there is two purposes to doing this, one would be to get the loot. I believe top score or high scores win bonus credits and the also win invisibility magic in a certificate. Sorry it has been a while so the prizes may be different. The other reason would be to say hey look at me.