This puzzles many people. The evidence is fairly incontrovertible that stock-picking and fund-picking are very, very expensive hobbies. So why do people do it? A fellow alum of the Chicago GSB once pointed out how many of our classmates, having spent $100K to learn that they can't beat the market, are now in the money management business. "I'm not sure," he said meditatively, "but I think maybe they should be in jail."
Why do people do this to themselves? My tenative answer is that you can't hit a home run with an index fund. You may get rich, eventually; but you will never get richer than everybody else. People investing in the stock market are buying the fantasy of the quick score. And like everyone else looking for a painless way to get rich, they're easy marks for the unscrupulous.
This article available online at:
http://www.theatlantic.com/business/archive/2007/12/why-do-people-buy-mutual-funds-or-individual-stocks/2370/