Minecraft wiki entry for Player_versus_Player, associated text: Think about it like this. With lots of people on one side, as well as regeneration from a full hunger bar slowly healing each player (and health potions), the whole army in general is almost continuously regaining health. (If your army's hunger bar isn't full, you shouldn't be in a battle!) Since all the opponent's damage is not placed in a concentrated area, every person alive is in a sense helping heal others. When someone dies, their regeneration and health is lost. So is their ability to fight, and the formation they were in is weakened, so momentum in terms of a steady advance is lost. Therefore, minimal life loss is the goal throughout the battle.