Personal appreciations aside, I'd Robin was actually pretty carefully adapted in Batman Forever. Are there elements that seemed a bit silly? Sure, but I don't think he was ever reduced to a joke here. His origins, conflicts, and growth are all there.
And if Nolan and Snyder only alluded to him, one could say that it was simply because their creative ambitions lay elsewhere, rather than for any other reason.
Just as many fans hope for and have ideas for a live-action version of the Robin, in all its glory and nuances, there are directors out there who feel the same way. And it's only a matter of time before they get the chance to bring their vision to life.
Actually, we know there's one who's ready to go if it weren't for a mix of studio scheduling issues and other creative wanderings...
OT :
Don't take this as a defense of the guy specifically, but there's always a stray bullet for Snyder somewhere in here, it's seriously becoming a running gag (or a compulsion?).