Without the back story, Batman is nothing but a billionaire lunatic running around a city in leather pants. The death of his parents at the hands of poverty and corruption mean we can at the very least understand Bruce Waynes extra curricular activities. Its important to remember there will be a good few young audience members who will never have seen Bats throw a punch before. Its therefore imperative that they have at least some understanding of why this man dresses like a Bat, and mentioning Thomas and Martha is the easiest possible way. While its unnecessary to retread ground walked in Batman Begins, it is central to the character of Batman that he himself and the audience remember exactly what started this crusade, and a brief mention here or there would be a great way for us all embrace the new Dark Knight with open arms.