Money is tight in Hollywood. People are going to the movies less. 2014 has had a record low of movie tickets in decades I believe. It makes sense for studios to try to bank on hard hitting big budget franchises targeted at a world audience. Why give 60 million to an established duo if there's no guarantee it'll be a success?
A big problem i've got with the "hollywood makes too many adaptations/too few original stuff" argument is that, why does it even matter? A lot - actually, I would wager, most - of the best films ever have been adaptations: 2001, Planet of the Apes, Blade Runner, To Kill A Mockingbird, hell even stuff like Vertigo, were based on established works. Bringing stories to life has been films M.O. since day one, and it's one of the most magical elements of the medium.
