Does The End Game Really Matter?

This post over at MPOGD.com has me thinking; does the end game of an MMORPG matter at all in its ultimate success or failure?

If you take the raw number of players that actively participate in end game raids in World of Warcraft and simply remove them from the total number of subscribers, World of Warcraft would still hold several million players. So, doesn't that mean that World of Warcraft would be popular without that end game content? Seriously, it is estimated that less than 2% of WoW's NA/EU user-base has actually stepped foot into an end game instance.

World of Warcraft is just one example, both of a game and of an end game model. What other models are there and what do they mean to the game as a whole?

Please discuss.