I've never bought the argument, although in the absence of any hard evidence it's difficult to say.
From the banks' perspective, they're going to charge more if they get into car leasing because they're not doing it to provide incentives to the consumer to buy a car. They're doing it because it's a financial product on which they want to make money, just like any other financial product, whereas the acceptance companies—and by that I mean General Motors Acceptance and the Honda acceptance company and so forth—are a captive arm of the automotive manufacturer and they're trying to move cars.
I've never understood the dealers' criticism, because they will get better rates and they control who they put the deal through at the dealership.