Leaving out split-screen co-op capability in Halo 5: Guardians was a rather controversial decision for developer 343 Industries, a mistake it plans not to make in the future.
"When we didn't put split screen in Halo 5, it was incredibly painful for the community and for us," 343 General Manager Bonnie Ross said at a presentation at DICE 2017 (via GameInformer). "I think it erodes trust with the community, as the community is a part of our world building."
Ross said that it has learned for the decision. "For any FPS, we will always have split screen support going forward," she said.
Originally, Xbox chief Phil Spencer had said back in 2015 that split-screen was not included because everyone was playing co-op online and not sitting on the couch with friends. "We see the robustness of what Xbox Live is today and where people are playing across Xbox Live -- you at your house, me at our house," he said at the time. "We know that's the vast majority of the co-op play. With Halo 5, the team really wanted to focus on making that experience great, both visually on the screen that you're looking at, and all the systems in place."