Say for the sake of argument there is a reset. A reset to what point? Does the movie end in with the birth of James T. Kirk and the proud father witnessing the birth and being handed his son for the first time? A joyous, happy moment? Basically a sign to the moviegoers that the timeline has been returned to how it was "supposed" to be?
I mean, for there to be a reset, Nero would have to be stopped at the point where he first polluted the timeline, right? Stopping him after he's committed all that mischief (47 destroyed Klingon ships, altering Kirk's life, maybe destroying Vulcan or some other planet) resets nothing. It's a new timeline. Those things stay. The future has been changed.
My point exactly: Nero has screwed the galactic pooch, and like Vader, is a consequential individual whose life and death affects the lives of untold billions of people across time and space. Kirk achieves heroic stature by stopping him (with the aid of Spock Prime acting as Obi Wan/Gandalf).
Setting everything back to zero as if Nero's actions never had happened would rob the entire $150 million dollar effort of any dramatic import. One might as well spend $150 million dollars on a Miley Cyrus vehicle. I don't believe that Orci and Kurtzman are THAT stupid.
Of course, we live in a universe where Shatner got to direct, so there you have it.