Except when it did. When casual players could run random heroic dungeons for valor points with which they could buy the second best gear in the game. That's when the game had a 12 million (stable) subscriber number. It took months to buy all the pieces so casuals had a reason to stay subbed and it didn't interfere with those who played the game seriously because they had that game for months already and most likely replaced it with the best gear in the game.