Because Battleship turned out to be such a great idea.
While Battleship isn't as bad as I thought it was going to be, it's still awful. And long. Really long. I guess if you're really looking for an action movie and are sick of The Avengers, Battleship might satisfy you for a little while. Even then, I'd recommend staying home and renting something.
But this is just one large cat's opinion. Will you see Battleship? If you do, tell us what you thought of it.