Nero went back in time to 2233. By changing things he created an alternate universe. Surely Spock, who fell into the black hole a few seconds after
Nero, should have been altered and be the 2387 product of Nero's new timeline rather than TOS Trek?
I guess you could say he was, because of his proximity to the black hole, unaffected in the same way the 1701-E was unaffected in First Contact just after the Borg went though their vortex-thing.
And T'Girl, what use is Spock in the Prime universe now? Romulus is gone, and his unification mission has failed. He's more use leading the surviving Vulcans in the altered timeline.
And to everyone who says "Go back and fix the damage done" - Nerada was the most powerful war machine in the universe. They barely defeated it once. Messing around could end with Nero destroying everything.
Also: They don't have the right. This Kirk's entire life is the result of Nero's tampering. It would be effectively killing him (and countless others) to undo it.