Could a slighlty poor US book office taking be down the later relase date and to word of mouth about the quality/issues of the film from places like the UK.
That might have played a role in convincing some less enthusiastic fans to wait for DVD, but probably not a huge number. Likewise, there were bootleg versions of the film out on the net because of the staggered release that might have hurt the box office a bit, but I still think most people want to see a big spectacle film like this in the theaters.
I was determined to see it because it was Ridley Scott doing scifi and revisiting the Alien
universe again, regardless of some poor reviews by some of our British (and other foreign) posters whose opinions I trust. And it was still worth seeing it even with the unfortunate sucktitude of the story.