User blog comment:Crazy sam10/Call of Duty Franchise sale on Steam Aug 28th Sep 1st 2014/@comment-5290320-20140829025008/@comment-5596583-20140831033503

I cannot claim expertise on the subject, as I've bought a grand total of one (1) game from Steam. However, it installed MW2 singleplayer and MW2 multiplayer as seperate games, presumably for reasons of connecting to the server on one and not the other, or something.

...Okay, I really have no idea why. Just that it does.