Movies are a business, and ultimately they need to make money. Star Trek at the theater was a sinking ship before 2009, peaking with First Contact wit a substantial fall-off with Insurrection before Nemesis flat-out bombed. Only Voyage Home way back in 1986 crossed the $100 million mark at the box office. And the franchise's records with new ships and new crews is spotty, at best. Next Generation did extremely well, but Deep Space 9 never found its audience until DVD and Voyager was weak. Enterprise wasn't exactly loved either.This is not a franchise studio execs had much faith in, and with good reason. New ship new crew without any recognizable characters would probably never have been green-lighted in the first place, the ROI just wouldn't have been there.
So I can definitely appreciate the choice they made. Kirk, Spock, and co. are iconic. Next Generation was loved by many (myself included), but the original crew on the original Enterprise IS Star Trek in the hearts and minds of the mass audience. The current choice allows them to shed the continuity problems of 28 seasons, 10 movies, and countless books (and yes, I realize the books aren't officially canon) filled with minutiae that's far too easy to stumble upon. Instead all of that still exists without anything being discarded. They can go back and set more books or even another TV series in the Prime Universe without a single issue arising, but the movies are now freed to do whatever they want without worrying about contradicting an episode of TOS.
So yeah I have little doubt that going back to the original characters was the only way we'd get a new Star Trek movie at all. At least the writers had the courtesy of leaving the original continuity completely intact and setting this in a new universe instead of simply throwing it out entirely.
For the "origin" of the crew there was very little continuity to worry about. The books and spin-offs are not even a consideration. At best they had maybe 2 - 3 episodes that had vague references so it was pretty wide open to do without having to CHANGE the characters completely. This is the biggest problem I had. It was lazy writing with cheap shock values thrown in.
It's interesting to note that (I hate to do a Star Wars comparison but...) when Lucas changed Han Solo to not fire first, everybody was in an uproar because it IMPLIED a change in character. In Abrams' movie they explicitly change the characters completely(with the exception of Bones who was closest to the original) and the majority are ok with it.
They have set precedent. The "prime universe" is now in the past and over-written. For all intents and purposes, this new "timeline" in the new prime universe and everything that follows will be based and referenced on that.