There have been many people who have taken on the role of Robin over the decades, so it's not absurd to think that Nightwing, it turns out that's not the case at all.
Every Robin has brought something unique to the role: Dick Grayson was the first in the role and continues to be one of DC's most prominent heroes, Jason Todd brought a sense of hopefulness, and Tim Drake is an outstanding detective who approached things from a smarter angle. All of these things made each Robin unique — including Stephanie Brown and Damian Wayne — so it's not unreasonable to assume that Batman would have a favorite iteration. Usually, Dick is known to be the best Robin — but he's also one of the only Robins to be fired from the role, and for seemingly no reason.
Batman Fires Dick Grayson from Robin
Dick Grayson was fired from Robin (for the first time) in Batman #408 by Max Allan Collins, Chris Warner, Mike DeCarlo, Adrienne Roy, and Todd Klein. After Dick fails to get the drop on the Joker, Joker manages to shoot him through the shoulder, badly injuring him and knocking him off the building. News stations actually start reporting that Robin was dead. Spooked by this event, Batman fires Dick from Robin, stating that the job is simply too dangerous. With that, nineteen-year-old Dick Grayson was no longer Robin, and the Robin mantle was retired. But what Batman would do only two days later throws these events into an entirely new light.
Later in Batman #408, Batman meets Jason Todd as he's stealing the tires off the Batmobile. Batman ends up adopts Jason and gives him the role of Robin in Batman #409 by Collins, Ross Andru, Dick Giordano, Roy, and John Costanza. This happens two days after he fires Dick. It was later retconned that Bruce simply missed having a Robin, so, rather than ask Dick to return, he found a replacement. But this excuse doesn't exactly make sense, considering the short timeline. In fact, in Nightwing: Year One (by Scott Beatty, Chuck Dixon, Scott McDaniel, Andy Owens, Gregory Wright, and Phil Balsman), published after the universe-resetting events of Zero Hour, the reason Dick was fired was changed.
Dick Grayson Is Fired from Robin (Again)
Instead of Batman worrying about his safety, Robin is fired in this Year One story for spending too much time with the Titans. Batman is unhappy with Dick's performance, and it's possible that this is the same reason pre-Zero Hour as well. Dick had faced many dangerous situations as Robin, but being shot once by the Joker is where Batman drew the line — only to immediately recruit a new Robin. This series of events doesn't make any sense if Batman was truly concerned about Robin. It's possible Batman just wanted a better partner. Dick Grayson is one of the greatest heroes in the DC Universe, and there's no denying what an amazing hero he is as Nightwing. But it seems Batman wanted something better from his Robin.
Check out Batman #408-409 and Nightwing: Year One, available now from DC Comics!