What current MMORPG's share is that you start the game as a low level player, gain XP, level up and reach the top. Getting there is a long trek, wich some may never complete but when you arrive then that is it. Just sit there, re-do the same grind over and over with only the top level content offering any kind of challenge and wait for an expansion to raise the level limit.
So what could change this, and why should it be changed?
Death could change it and for the same reasons it exists in real life, to kill of the grumpie oldies and make room for a fresh new generation.