That would have been 400 times cheesier and everyone would have know what he was from the start.
This version of the character wasn't as literal or directly ripped from the comics, but still shared MANY of the same characteristics (orphan, bond with Bruce, inspired by Batman, fights alongside, believes in Batman's mission). Blake represents the living embodiment of a 'Robin', someone who earns the trust of Batman enough for him to be allowed into his secret world, and someone who may ultimately carry on Bruce's legacy one way or another. Will be take up the mantle of the Bat? Will he embrace his true name of Robin and create his own persona? Will Bruce ever need to return to Gotham to face another threat and fight alongside him?
We don't know, and that's the fun of it.