"Whenever you feel like criticizing anyone," he told me, "just remember that all the people in this world haven't had the advantages that you've had."
-- Quote from The Great Gatsby
"Not all the people in this world have had the advantages that you've had" makes more sense to me, or it literally means "all the people not"?
The sentence is stating not all people have had his experiences.
The negative was probably an oxymoron (a negative word put beside a contrasting positive). This is an English writing concept to give contrast and keep things interesting. The oxymoron here would be the contrast between "haven't" and "had".
Hope this helps.
So basically: the odd word order oan because it sounds cool and yes it means that not everyone has experienced the same things as him.
:)
Everyone does not have something.
Not everyone has something.
They both resolve to a negation of the predicate "everyone has something".
