1. Anti-addiction: When you don’t pay a monthly subscription for an MMO, you no longer feel the obligation to get “the most for your money” out of it. In times when “gaming addiction” is a topic of mass media discussion, not paying for the game allows you to tear yourself away from the keyboard and remember you have a family (and friends, if you’re lucky!).
I like how they don't mention cash shop addiction in most F2P games. (-cough- Trickster -cough-)