Last couple of replies have summed it up.
And Vahn's Ego.
And what do I mean by Vahn's Ego? Well he was so anti-quickscoping before Black Ops 1 even released and now yet once he gets people to bend over for him, he enjoys it. Enough so to show him doing it, not to mention a Easter Egg for an OpTic Sniper member in that MP reveal trailer.
Besides, quickscoping gives the game more publicity since they tend to get watched more than the normal game play videos.
I think i's mostly because of the small maps.
Taking it out does not change much though.
I mean BO1 did not have QS right? People just drag scoped and still there were complaints about QS.
I like that it's in the game and not because I do nothing but QS. It's more of a panic shot if you don't have time to grab your secondary.