There was a time a few years ago when every single-player game was thought to 'need' multiplayer in order to be successful. With the idea being that nobody wanted to play single player-only titles and wouldn't stick around if they couldn't jump online every day, developers and publishers - regardless of whether it made any sense or not - began crow-barring multiplayer into everything.
Of course, almost all of these added multiplayer elements turned out to be nothing but terrible time wasters. The likes of Dead Space 2's monster vs human gameplay or Spec Ops: The Line's frantic deathmatches could have been great additions if the multiplayer was the focus from the start, but most of the time you could tell the developers put in as little effort as possible, just so they could boast about having an online feature on the back of the box.
But while these big-name disasters set a terrible precedent, not all multiplayer suites in predominantly single-player experiences have to be underdeveloped afterthoughts, and in many cases this stigma surrounding the online modes of great narrative titles has led to some of the greatest multiplayer experiences of the past few years being completely overlooked.