The system is supposed to punish players who have been kicked or have left. Some players are kicked for being low level or not very good in which case they don't deserve the timer. Players that are kicked for going AFK for too long or are being abusive do deserve the timer. Players who just leave could have something more important to do (in which case the timer is irrelevant to them), have decided the group is too shabby (they deserve the timer), accidently went into the wrong dungeon or was receiving abuse (don't deserve the timer). Its impossible to distinguish between all of these scenarios so instead of punishing everyone the only fair thing to do is get rid of the timer.