When you're the market leader in MMO games, you can afford to do a little innovating – though not so much as to disturb or ruffle the customers you've already acquired. When you're making a top drawer MMO with thirty million dollars of other people's money, you can't afford to innovate. Refinements, sure. But no big risks.
So where's the innovation? These days, you see it in the free to play genre, and its close cousin, the "freemium" game. Both of these games make their money from microtransactions. In order to get a customer to fork over a microtransaction, these games require customers that are vested into the world.
But free to play means the player has invested nothing but the time spent downloading the product. And there's a perception among some industry professionals that "easy come, easy go."