I agree but you and I both know that'll probably never happen. IIRC, most people who buy the yearly installments of the CoD don't even touch/complete the single player. (I always play and beat the SP part first, then I move onto the MP.)
I'm surprised that they haven't added MP to the Fallout series yet. (Altho I'm not sure how that'd work out...prolly something like Stranglehold or Max Payne 3.)
Unlike most people on XBL, I enjoy a good ol' SP game such as Fallout 3, GTA IV or Mass Effect 2. I love games which offer me a lot of content (50+ hours to complete) which gives me more bang for my buck.
Why not? =O