I agree that some of the hi-end psycho babble, usually overseas based gurus are not worth their hype, but how do you explain why in sport, high performing athletes/teams totally rely on their coaches? As do many high performing Executives - not the ones you read about in the papers but the ones who are transforming their organisations without the media hype.
Everyone can learn from other people, and having a mentor is one of the most powerful ways of learning from the experiences of others. And knowing some of these coaches, their motive is altruistic, and passing on their experience and learnings to others is one of the most fulfilling things you can accomplish in life. At least, that is what the good ones think!
Coaching yourself will have a totally different outcome; while obviously learning from your own mistakes is important, sometimes you just cant see where the mistakes are. And sometimes it is also important not to re-invent the wheel
And like everything in life, there are always good and bad practioners in everything.