For every one of those fucked-up rich white kids, hundreds of non-fucked up ones go on to lead highly successful lives.
The reason the stereotype is so well-advertised is because:
1) To the older generation, it's almost inconceivable that someone would blow a lead on life like that. It's the equivalent of starting every inning with a man on third and still not being able to score.
2) People love talking about train wrecks.