Because many MMO developers have put more focus in "level grind" than in end game features this not mean that end game must be "pointless extra content" and leveling the only reason for play. Once upon a time that some MMOs don't have mandatory levels or end game, games how SWG, UO, EVE were -and are- world games where gamers changed the landscape of the game-world in some degree, in these game grind a character is only a part of the game, also you can create a crafter bussines, build a city, decorate your game house, participate in PvP attacking other faction o enemy guild bases and instalations, etc.

Oriental MMOs and WoW succes changed that, MMOs lose their variety and all new MMO become level based EQ/WoW type MMOs, consequence: burnout, the only and one thing people do in current MMOs are kill for xp and loots, do repetitive quests for more xp and loot, do raids for more xp and loot, and do PvP for more xp and loot. You detect some repetitive patting in this formula, true?

Character progression is an important game piece, but "level grind to reach end game" is bad character progression, for that I said the level grind is not the game, and reach the end game is not the MMO objetive. Because all the game must have many replayable features, build things and not kill and destroy forever, create a character history througth game changing events, a never ending progression, but now all MMOs are repetitive and lineal.

The most of the people dont reach the burnout stage and leave MMOs for "get a life" reasons, they continue playing off-line game for many hours to day, the leave for simple and plain BOREDOM, doing the same repetitive and lineal tasks for hours is not precisely a gratificant playtime, is not escapisn is a boring and repetitive work, very similar to many real life works, when people lose contact with their in-game friendships and guild relations only remains that truth, and that is the reason for burnout and leaving.

For return we need MMO with less kill-kill-kill and more constructive features.