Because it is the same fucking thing repeated over and over again over a period of weeks if not MONTHS, that you pay for continuously and have to continue to pay to experience any part of the game no matter how much time you put in.
Frankly, I played WoW to level 63, and got bored to fuck with it, I also took part in the 2007 tournament payed for update and have made many "alts" of different races, classes and talent trees.
Same. Damn. Thing.
Here is a fun packed guide to how you will spend an average few hours on WoW:
1: Get some quests by wandering around an area right clicking on friendly NPC's
2: Compleate said quests by right clicking on enemy NPC's, DON'T FORGET TO ADD BUTTONS 1-4 OR ELSE UR DOIN IT RONG
3: Hand quests in for "l33t lewt", monies and experience
4: Get an instance group together for lewt and/or money.
5: Do said instance by either spamming heal spells or by doing the same as step 2
6: Get enough xp to go up around 66% of a level
7: Do some crafting by left clicking on some things in a list, You might have to buy ingrediants using In game money
And before you yell "OMG H8R1!111!" I really do wish I could enjoy WoW, I really do, but I simply can't when they ask me to pay £9/$15 a month to repeat this formula over and over again, let us not forget that on your first year of playing you will spend around $195 on this game (1st month + original is free from www.trywarcraft.com then add Bc expansion $10, Wotlk expansion $20 and then $15 a month for 11 months, $165)
For that you could buy 10 games if you were a "smart shopper".
10 games or WoW for a year? Your choice.