Well, why? I mean for the Xbox I understand. But for the Pc you really don't have to, considering the fact that Left 4 Dead 2 has all of the DLC's including all of the L4D1 levels with it for FREE, and still $20. I mean maybe people just like the weapon better in this one, I understand. Maybe people just like the design of the common and special infected, I understand. But Left 4 Dead 2 also has a steam workshop to download mods. I mean this is my opinon, but to me I think it's kind of a waste of money.