Re: I'll never really understand...
"... he seems happy enough. Some people are stuck in low-paid dead-end jobs."
Some of us prefer to be left alone to get on and do the job we are paid for, not endlessly chasing the next "career goal". Let's put it this way - which path is most likely to lead to burnout and dissatisfaction? I've done both, and, whilst I miss the travel in some ways (e.g. to have a good excuse to escape the children occasionally, if nothing else!*), I really don't miss the endless reviews and bloody interviews that come with chasing the next level of distance between what I'm good at and what the post requires. Good luck to those who want to do that, but it isn't for me, or your friend.
* A simplified life of work, food, read, sleep, even in a hotel room I didn't choose, sounds very attractive at the moment :-)