The reasons are many:
- It had to work as a standalone adventure, meaning a fresh start.
Which requires no cadet to captain.
- It had to be faster paced, which means the story strictly known to Canon would not have worked.
Bull. Faster paced does not require the sacrifice of canon, let alone cadet to captain.
- It had to to start with Kirk's youth, and end with him as Captain, again not possible with the linear story within Canon.
Which of course, makes the choice of a "linear" story, a BAD choice.
It wasn't actually handed to him. He had to fight through this movie to earn his place:
- He had to convinve Captain Pike about the nature of the Romulan attack.
Bull. His "convincing" first had no functional logic to it whatsoever. It's pure luck that he was right. Further, his convincing did absolutely nothing to the movie, because the whole reason he tried to convince Pike was so they could drop out of warp well before Vulcan and take a tactical assessment of what's going on around Vulcan and not "land in the (non-existent) trap." However, the moment he convinces Pike this indeed the case, they arrive at Vulcan, land in "the trap", and thus his convincing was utterly pointless and meaningless, and thus had no need to do it.
- He had to get Spock to reveal he was emotionally compromise.
And totally failed at it, as he first had to commit insubordination, attack a superior officer, get thrown off the Enterprise and learn to love the snow, and fail to notice old Spock's senility.
He could have pointed out Spock's irrationality (and I suppose stupidity) by simply calmly pointing out that a. wherever they were going they should be doing it at warp already instead of limping bout at sublight speeds, and thus that Spock isn't thinking straight, and then b. that now the Narada is gone they should be able to contact the fleet by subspace radio, as opposed flying all the way to it, before telling them what's going on. Thus if they do decide for the Enterprise and the fleet go to Earth together, they at least can decided a rendez-vous point much closer to Earth, as the fleet can already start for Earth.
But he was too much frothing at the mouth to be able to perform simple logic. Kirk is every bit as emotionally compromised as Spock is; in fact if the reaction to the destruction of Vulcan is normal, EVERYONE is emotionally compromised, which rather makes trying to show Spock is emotionally compromised rather pointless.
- He had to work with a crew who had no reason to respect him in order to defeat Nero, and save Earth and the Federation.
That's a hell of a lot to overcome.
That's because he's an asshole. Yet nowhere did he even for once have to prove himself to them, or even show a hint of leadership ability, not even a speech to convince them. Meaning he did not grow, he learned nothing, everything got tossed to him on a silver platter, and he did not really overcome anything.
I suspect this may be partly true. The movie could not guarantee sequels, and yet had to be set up so that sequels could be made.
The film also had the requirement to show the basic construct of Star Trek. That means, by definition, Kirk as the Captain by the end of the movie.
A simple promotion to Lieutenant instead of ensign, and then a "seven years later" caption would have done that just fine.
From the Studio, the return on investment was the primary focus.
From the filmmakers, making a good movie that achieved this goal was.
The "Bad Art" argument is not that applicable to those who do not believe this movie was "Bad Art".
It was not a Picasso Painting from a Shakespear play.
It was not a good movie, it was a horrible movie, that despite that made money.
Fortunately or unfortunately, it's done and over. I am looking forward to XII, which should be a much freer project. XI was tough to pull off. At least they did it in a fun way that was successful enough to bring another film which will hopefully have some more depth to it.
I share this sentiment. XI had some things done out of necessity, even if that necessity is not always seen.
XII now, thanks to XI, has an effectively clean slate.
Ah, yes, "Just wait till the next movie."
Ain't gonna happen. This pile made money. The next movie is not only going to be more of the same, it'll be worse. Just like Transformers 1 versus 2 by the same writing team.
3D Master said:

Oh, there's a lot more than
one. By the way, several have already been named.
Again, name them, because I haven't heard them. I'd like to know which movies you consider worse, there's a chance I've seen them, and I'll tell you 'no', and why not.
I've seen The Asylum movies ripoffs, and they're better than JJ Trek, all of them.
3D Master said:
There's a fleet, then there's a planet-wide defense grid.
The information needed to bypass Earth's defenses was given to Nero by Pike.
No, Nero got the codes to shut down the solar systems AUTOMATED defenses. Which rather shows again the total incompetency of people in Starfleet. Seriously, if you do not know how to program a defense system that is capable of recognizing Starfleet ships (and we suppose civilian liners and merchant ships) you're an incompetent moron! Why else would a captain of a ship carry the command codes to turn off an entire solar systems defense systems? Because it gets blown to bits if it can't turn them off.
Of course, that doesn't really matter. Because even if being able to shut down an entire solars system's defense systems with some command codes isn't idiocy enough, there would still be MANNED MANUAL defense systems. And if not, then they're once again idiots, because whoever trusts the security of your capital world to an automated defense system only that can be hacked, and even more so one that has ways to be remotely shut down built in, are idiots.
This movie is mind-boggingly bad. I know how bad it is, and I still can't believe just how bad it is. With the exception of two scenes with Spock, it's just nothing but plot-holes, idiocies, and what not.