Well, its very simple to see why. It doesnt have a demographic.
becuase i work at a theatre, and a busy one for our area, i saw the rundown of demographics and it went something like this:
DISCLAIMER: The demographics of this post are only representable at the theatre I work at, and I can not speak for other theatres in other regions.
Eat, Pray, Love: Old People, Mothers who did not want to see Expendables iwth thier significant others, Overly homosexual people (you know who i mean, andi have nothing against them).
The Expendables: MEN (of all ages), Women who did not want to swallow the crap of EPL, anyone sneaking into a movie.
The Other Guys: People dating, People married, people who compromised between Expendables and EPL. Groups of people who could not get tickets to EXBLS and EPL.
Inception: Old people who saw Titanic, Old people who saw EPL, women who think Dicaprio is hot, people who think he is "talented" (he's not the actor Titanic made him out to be). Young adults who want to appear smart and give their analysis of a movie they THINK they understand.
Despicable Me: Children, Teens, Tweens.
Cats and Dogs 2: See Despicable Me.
Grown Ups: See The Other Guys.
Salt: well... really no one this week. Normally its just men and women who want to see Angelina Jolie get back in the acting business.
Dinner For Schmucks: People who have not seen it yet and LIKE Steve Carrol (yes, he is a deal breaker for that movie, suprising as it is.)
Step Up 3D: "Hood Rats", white kids who like to act black (accept you are not and MOVE ON!), anyone who thinks they are that rap or hip hop speaks to them (chances are, if you live in the suburbs, it doesnt.)
and finally Scott Pilgrim: People who like Michael Cera, fans of the graphic novel, fans of Juno, fans of offbeat teen movies who enjoy people like Michael Cera and Luke Wilson (you know, how they bring that dry witty sense of humour to the screen), whatever was left that couldnt sneak into EXBLS and do not like movies like TOG.
yeah.... i know, that sounds like i have no idea what i'm saying, and in reality, I'm not an expert, but that "whatever is left" demographical mix isnt a large group, and the movie sufers not having big name actors besides Michael Cera. Its just the sad, unfortunate timing of opening with the Overcompensating Expendables and the pathetically bland cookie-cutter romance movie with an A-list star.