Earth is big, and there are lots of other colonies, so something different would have been nice. Vaughn wasn't born on Earth. And you can't tell by a person's name what sort of culture he or she was raised in. There was a diversity of people and names in other series. I just want you to see my perspective.
People make career changes like that all the time.
You're right, they do. But he didn't. Well, remember that this is Star Trek . IF he'd had a mid-life crisis, it would have happened when he was 75. He's actually got some really good reasons for going no further than commander, which are revealed over the course of the books.