But I don't understand why they (Kurtzman and Orci) couldn't have just had Kirk call him "sawbones." Maybe I'm wrong, but it seemed fairly obvious to me.
You just answered your own question. Why should any writer be satisfied doing something that the audience would consider obvious and predictable? Where's the fun in telling, or watching, an origin story that has no surprises?
Because they are writing for Star Trek? If they want to be free in everything, they should be writing something original. McCoy's nickname being "sawbones" is not only canon, it also makes perfect sense. Their new "explanation" on the other hand, does not.
QFT.
The divorce bit works better in 2009.
Something can't work better if it doesn't work at all, and this certainly didn't for me. Of course, clearly, it did for a lot of other people, but to my ears, it was the clunkiest, most jarring line of the movie. Who says something like "she left me nothing but my bones?" Is that a common saying in the 23rd century?
I guess what really bothered about it (and why I wish they had just "explained" the sawbones thing), is that it really just seemed like they were flailing about desperately for some way to explain the nickname, and couldn't come up with anything. It just didn't strike me as sounding even remotely natural.
(But again, I'm apparently in the minority on that, so I guess all this is good for is a little venting.)
The real problem, I suspect, is that the term "sawbones" has largely fallen out of the vernacular. It's a bit of antiquated slang that would have required too much effort to explain.
Oh no, the effort.
QFT again! (In my opinion, of course.)
When you only have two hours to tell a story, why bog things down explaining what a "sawbones" is? Especially when it doesn't advance the plot.
That's just good editing.
It probably wouldn't have taken any longer than McCoy explaining about how his wife divorced him. That didn't advance the plot; it gave depth to the character. "Sawbones" would've been a natural extension of McCoy claiming to be an ol' country doctor, which would have been an opportunity for similar character advancement.
The "bones" line in the movie killed three birds with one stone: it explained the nickname, fleshed out McCoy's backstory, and got a laugh from the audience.
People laugh at that? I must have no sense of humor.
Or a very subtle moment where McCoy comes into Kirk's quarters at the Academy, while Kirk is reading Dickens' book and during that conversation he refers to him as Bones for the first time. No spoonfeeding, but you have the association to McCoy's actual profession (and not to his divorce, which is silly), you have Kirk's fondness for antiques AND even a hint at why Kirk could have been "a stack of books with legs" at the academy.
I could see this working for KirkPrime, but IMO at least, I really don't see either of those things being true of NewKirk.
I wasn't gonna bring this up because I was afraid I'd just sound bitter, but since you mentioned it... Yeah, "sawbones" would only work if there was any evidence whatsoever that nuKirk had an ounce of culture. Apparently, having a passion for learning and a fondness for times past isn't considered "cool" anymore.
...And yet in some ways it would be the same since their core personalities are essentially the same.
I'm going to have to respectfully disagree with you there. The ship may have looked a little different, circumstances may have been altered, but in my own opinion (in which I am, again, the minority), the core personalities was the factor that was changed
the most about the new movie. There's not really any way for me to "prove" that, but that was the point where the movie really left me flat.

Oh well. I apologize, because my goal in life is NOT to bust in on every STXI thread and try to convince everyone that it was terrible. It wasn't to my tastes, that's unfortunate, but I'm glad you all enjoyed it, and I still hold out some hope for the next one. So, I'm not trying to be negative, but it is nice to vent (once in a while), and hey, it is a discussion board...
The idea is to go boldly where no Trek novel has gone before.
Well, after reading the blurbs, the stories are not so much like that.
Never judge a book by its blurb. They're not written by the authors, and as often as not, they have only slight resemblance to what the stories are actually about (of course, I may just be jaded by how bad the ones on Netflix are).