This may seem overly negative or (internet) contrarian, and I believe yours is a good comment, but these are subject to political forces as much as--or more than--any.
Put your time in (not bankers hours), move when transferred, whoa this is a lot of paperwork, climb the ladder, spend time at HQ and "make friends" at all your stops, go along and get along, now there are kids and spouse/house and schools, do your 20 so you can retire, start new job in security or back to private practice thanks to your well-tended reputation, etc.
Who's gonna stick their neck out anymore? (Besides Snowden.)
Put your time in (not bankers hours), move when transferred, whoa this is a lot of paperwork, climb the ladder, spend time at HQ and "make friends" at all your stops, go along and get along, now there are kids and spouse/house and schools, do your 20 so you can retire, start new job in security or back to private practice thanks to your well-tended reputation, etc.
Who's gonna stick their neck out anymore? (Besides Snowden.)