I'm just the messenger
Respawn Entertainment's Titanfall will be a multiplayer-only game, and that wasn't a decision that the studio made haphazardly. Rather, it took into account player habits and its development team size, and realized its resources would be better spent solely on a multiplayer experience.
When talking to GamesIndustry International, co-founder of Respawn, Vince Zampella, said "And how many people finish the single-player game? It's a small percentage. It's like, everyone plays through the first level, but 5 percent of people finish the game. Really, you split the team. They're two different games. They're balanced differently, they're scoped differently. But people spend hundreds of hours in the multiplayer experience versus as little time as possible rushing to the end [of a campaign]."
Instead, Respawn will try to position itself to appeal to a slightly different niche than the already established shooters. Zampella added "Honestly, we're not shipping the same time as them. We're going for something different. We're not gunning for Call of Duty. We're doing our thing. The important thing is to make sure what we're doing is fun. I'm OK with Call of Duty being big. I helped create it, so I'm proud to see it's something so big that it goes beyond me."
Zampella: Titanfall "not gunning for Call of Duty" [GamesIndustry International]