Re: Someone please explain why....
It's also suggesting that no matter what, it's impossible to expect all citizens to come together to protect their city as a union of "good" to fight off evil. It's just impossible. There's always going to be people who are too lazy to do anything, cowardly waiting for the place to be fixed through the actions of others. There's always going to be people who ENJOY the bad that is happening. And there will always only be a portion of good people who will actually stand up.
So there's a ****load of work to do in Gotham. I think the idea is that perhaps once they're saved from an atom bomb and they honor Batman, a ton of them may stand up now. But that's only a portion. That's why Batman is still needed.
It's Nolans way of creating a young successor to the cowl, like Terry, but in a seperate universe. While giving a nice wink to the fans with the "Robin" reference.
It's a way of saying..
"yes this is an original character created for this trilogy but he is the epitome of almost every successor that's ever been under Bruce Wayne. We wont show you Batgirl or a kid Grayson/Todd/Drake/Kelly running around in a red suit, or a sci-fi Bats who comes back to the cave to see 80 year old Bruce with his dog Ace. But they all have something in common: the theme of passing the mantle. For the legacy to live forever through multiple generations".