Because most major films actually make more money overseas than in the US now. Studios don't mind bootlegging of films as much, because they know people don't like camrips, but if there's a screener copy leaked, they'll flip their shit. That said, the bootlegs could help boost DVD/BD sales down the road by exposing more people to the movie, so it's not a total loss.
Iron Man's record breaking $200 million weekend take seems to confirm that assertion.
No doubt, Disney is popping the champagne corks.