What has happened is dealers have tried to turn parts and service into big profit centers, 10-20% mark up over MSRP on parts, $100/hr labor rates, specials they want the service department to push, whether the customer needs it or not.
Then they wonder why their customers disappear. If they would realize service and parts departments create LOYALTY, and are their BEST salesman, things will be different.
They would rather drive customers away after the sale and then spend MILLIONS in advertising to get new ones.
You want a good dealer, he is the one that is busy but NEVER advertises, the dealers that advertise out the wazoo, do so because they can;'t keep current customers happy.