Very true. I can see both sides of the issue to be honest, but I'm obviously a little biased at the moment. lol Dealerships are a business, and they don't want to expose themselves to possible issues with privacy laws, and angry former owner.
I really wouldn't have any problem with the service records of any of my previous cars being disclosed to anyone that cared to find out, as long as my personal information was kept out of it. I would want want the potential buyers to know the issues their buying into. Perhaps a better policy would be to present owners with a privacy waiver when they trade vehicles in. If it is really of concern to you, you can sign it, otherwise they are available to the next owner of the vehicle.