The problem with comic book movies is that it has to condense 70 years of retcons, reboots, and continuity into two hours of cinema and still squeez a plot in there. They tend to aim for the proverbial lowest common denominator--in this case, the general populace who doesn't know the characters' histories like fans. Everything has to be dumbed down for those who are unable or unwilling to follow years of history.
Which is why Batman Begins retold Bruce's origin story and why it introduced Ra's al Ghul gradually instead of having him be the kind of figure he is in the comics.