User blog comment:Callofduty4/Black Ops III Zombie reveal at SDCC/@comment-1263839-20150625205941/@comment-24756040-20150626041930

Because it's among Treyarch's most defining features, and is one of the core factors going for Treyarch's Call of Duty's. I can see why people would judge the game from its zombies; however, I wouldn't think that Zombies is the sole core of Treyarch's legacy in Call of Duty.