http://arstechnica.com/gaming/2009/04/demigod-hit-by-massive...
IMHO, DRM causes there to be a delay (provided the game is not leaked) between game launch and game available for free on the internet. When your target audience is known to be... impatient... that might make a lot of difference. Unfortunately it comes down to not being able to trust your own audience, as the author said. I would prefer DRM free everything as well, but if the economics support it, it would be pretty silly to ignore that.