Explanation, please

In a New York Times report on the resurgence of classical music on public radio stations . . .

http://www.nytimes.com/2010/04/26/business/media/26radio.html?ref=business

. . . Elizabeth Jenkins obtains this insight from Marc Hand, managing director of the consulting firm Public Radio Capital:

"Classical audiences have an average age of 63, Mr. Hand said. 'In the commercial model, that’s not at all an attractive demographic for advertisers,' he said, but for a public broadcaster, 'it’s a great demographic for membership,' a passionate group with disposable income and a disposition to contribute."

Would someone care to explain why an audience with money to spend is "not at all" attractive to advertisers?