Its the Barton Fink effect, the studio goes after people who have big names but can't otherwise get anything else off the ground. It doesn't matter that their resumes in no way mesh with a dinosaur-eating-people adventure flick, get me that dude who wrote Citizen Ruth!
David Mamet remains in the arthouse ghetto with his actual films, but he's got credits on shitloads of 'real' studio pictures. Same with Noah Baumbach, Alexander Payne, and god only knows how many others.