Doesn't really surprise me, I've been saying this for years, still: a research conducted on Steam (though I can testify this also goes for consoles, if maybe a little less dramatically) reveals that most gamers never complete the games they buy. Only half of the Steam users who own them have completed Mass Effect 2 and Bioshock Infinite, much less than half has completed the 2-hours Portal (a Valve game no less), same goes for Arkham City. Also, only less than 1 Steam user in 3 has finished the main quest in Skyrim and Borderlands 2.
Don't like to repeat myself, but do you see why single player is being put aside by developers? Because even when games have kickass campaigns, people don't play them. Prepare for a future with nothing but CoD clones and identical MOBAS, people.