Also, having played MOST of the CoD line up to date (missed Ghosts, BO3, and Infinite Warfare), I am really disappointed that the developers chose to get rid of the campaign. While it could be argued that this was a space saving thing, I'm a bit more cynical and see a few different reasons:
1) The actual story campaign is a full game price DLC, similar to how you could buy BO3 multiplayer by itself.
2) The campaign was left out so that the profit margin from the game would be larger, especially once loot drops go live.
3) CoD developers want you to buy the new CoD every year, therefore, having a good story line would be bad, as you might not want to play the new game if the story looks dumb. If they continue with no story mode, then the new players might not have a reason to keep from buying the 1 CoD per year.