Probably because DC has established that he can.
Theres this worry that DC is toning down what she can do recently, but this is not a new problem.
Back during post crisis there was that utter piece of crap 'Superman Batman Wonder Woman: Trinity' where Diana served as a damnsel for Superman and Batman to take turns saving which aside from other classy moments like Ras Al Guul effortlessly defeating her and killing hundreds of Amazons and declaring he would make them all his sex slaves, we also got Bizarro snapping the lasso in half followed by him mopping the floor with Wonder Woman, leading to Batman beating up Bizarro effortlessly
http://i253.photobucket.com/albums/h...zaro_vs_WW.jpg