I think I play these free weekends because I like the texture diversity in the Call of Duty games post-MW2. There's really pretty fancy parts in some of the maps.
It's certainly not for the guys who are seeing through walls and spawn camping with endless killstreaks. Though those dudes tend to get really upset when you start kamikazing with grenades and rocket launchers because half your team has left. This guy who was like 86-1 and kept calling in airstrikes every two seconds told me to "play the right way" because I was blindly firing rockets at all the crap in the sky and then blew up like three of his clanmates trying to cap a point with a suicide bombing one time I managed to get more than five feet from spawning.
I was like "go fuck yourself Larry Brown."
And got a sweet ass badge or something plus like a billion thousand XP for killing three dudes with a nade.