Why Battlefield 4 doesn't have co-op, but future Battlefield sequels might
“We were just stretching too thin” on Battlefield 3, says DICE.
Battlefield 3’s standalone co-op component was a bit of a mixture – one part smart tactical infiltration sequence to one part fatally skill-dependent helicopter madness. Battlefield 4 has accordingly shifted the focus squarely to the competitive multiplayer and campaign, as DICE considers this a more efficient use of resources. It may return to the idea in future, however.