Lots of churn brings people in and out, and the potential for high salaries act as a beacon that draws many talented people to the industry who would otherwise

Lots of churn brings people in and out, and the potential for high salaries act as a beacon that draws many talented people to the industry who would otherwise have done something more fulfilling. They're much more about recruiting and marketing than rewarding performance. See also Freakonomics about drug dealers and McDonalds for a more detailed explanation.