Cause Snyder is still a 15 year old boy with dreams from reading comics in the 80's (Miller's TDK) and thinking how cool it would've been to see an older beat up brooding darker Batman on screen. The problem is, he didn't realize that The Dark Knight was a stand alone elseworlds story line that did not take place in the ongoing DC universe comic books. He even modeled his depressing Superman after the Superman in TDK as well.
Affleck Bats was way too big and muscular. Just like in the TDK comic. Bats needs to be more slim and agile like an olympic athlete and martial artist. Not a big heavyweight Mr. Olympia muscle man bruiser weight lifting champion. The real comic Batman fights with grace and speed , as well as power, as being one of the best Martial Artist's in the DCU. Not a street brawler who overpowers his opponents. The fight scenes in the movies show it too. I know people like it, but watch how slow and stiff he is in the fight scenes. The rooftop battle in the beginning of JL with the Parademon is awful. It's such a slow non agile movement scene. Part of it may be do to the design of the suit, but it's still pretty bad.