This could be considered related to - but definitely not the same as - What are the advantages and disadvantages of develop in play (DIP) compared to develop at the start (DAS) character generation?. For this question, I'm interested in focussing on the method and results of "Prior Career"-style generation, where you end up with a character that has a "partial backstory" and skills, vs. what I call, in my biased fashion, "Throw the kid in at the deep end"-style character generation, where you start with a character that may have certain aptitudes, but no actual skills to speak of.
I get that "deep end" character generation is likely to be faster, and that the idea is to play the game, not spend a session rolling up characters. I also get that you'll develop the skills in play. Why would this be considered advantageous, aside from the metareasons given? As near as I can tell, "Prior Career"-style generation is pretty much limited to the various incarnations of Traveller; why has this sort of chargen not been taken up by other systems/genres?
1st edit: I'm not looking at development of the personality of the character, as the DIP vs DAS dichotomy seems to emphasize; I'm looking at the contrast between mechanics.
2nd edit: After seeing the discussion that the unclearness seems to have prompted, I'd have to say that the question is ultimately less about advantages/disadvantages of a specific mechanic, and more about advantages/disadvantages of chargen that starts you with a skilled/experienced character vs. chargen that throws you into the game with no experience.