I blame Wii Fit
This is only half a joke - I am sure that though probably not anything close to the main reason, IW's refusal to work on the Wii versions of MW, even though Activision wanted these versions, didn't exactly help.
Currently Playing: Shin Megami Tensei: Devil Survivor Overclocked, Professor Layton and the Curious Village
Anticipating: Xenoblade, The Last Story, Mario Kart 7, Rayman Origins, Zelda SS, Crush3D, Tales of the Abyss 3DS, MGS:Snake Eater 3DS, RE:Revelations, Time Travellers, Professor Layton vs. Ace Attorney, Luigi's Mansion 2, MH TriG, DQ Monsters, Heroes of Ruin