The Far Cry series, to the best of my knowledge, has never been big on multiplayer. The option is there for those who want it and it's apparently decent, but I suspect only a small slice of the Far Cry audience actually bothers with it. The sprawling, open-world settings are clearly designed first and foremost for a single-player experience. Presumably with that in mind, Far Cry Primal is dropping multiplayer, including co-op, altogether.
“We are focusing entirely on creating the best possible Far Cry experience for our fans. Bringing the Stone Age to life and providing players with a strong gameplay experience based off of the Far Cry legacy meant we had to reinvent our core gameplay loop. This was definitely not a small undertaking,” Ubisoft Community Manager Jason Paradise explained on Steam “Our focus was on delivering this fantasy which required clear priorities for the team. Therefore, in the early stages of the project, we made the difficult choice of focusing our efforts on the single player experience.”
Personally, I'm a fan of single-player experiences and so I don't have a problem with that at all. But clearly not everyone is happy about it, particularly with regard to the lack of a co-op mode, which did seem fun in Far Cry 4. Primal is set to come out on March 1. Have a look at our hands-on with the game from early December right here.