Publisher Activision said that the feature was scrapped because the 4v4 multiplayer was prioritised during development, according to company blogger Dan Amrich.
"This is the first Call of Duty game on Vita, and it needs to deliver on its core strengths - arguably, multiplayer gaming with twin-stick controls in a portable format. That's the core experience, and that simply needs to come first," said Amrich.
"There's always a list of things you want to do and things you need to do, and at the end of the day, realistic goals are the ones that people actually attain."
Black Ops: Declassified's multiplayer will feature a Hostilities Mode with similar gameplay to the zombies maps. Players will go up against hordes of enemies, but these will be living foes rather than undead.
Call of Duty: Black Ops: Declassified is released for PS Vita in November.
> Read Digital Spy's preview of Call of Duty: Black Ops: Declassified