Studios make movies so they can fill seats to print money to make more movies to fill more seats to print more money. And the easiest way to start printing money is to go with an established movie franchise. Like Superman! But the real reason we need a new Superman movie (as opposed to needing a new Spider-Man movie) is because the last one, Superman Returns, was so bad.
Sure a little money for the studio wouldn't hurt either but just watch everything that was wrong with it in 6 minutes.
It's A LOT going bad. Hopefully Man of Steel fixes it! [CinemaSins]