Go look at a car from the 90s with a DIN or double-DIN stereo, then go look at one from the past five years, where the prevalence of nonstandard sized stereos has gone way up, as has the complexity of how tightly coupled they are to the rest of the car. Those are the hoops. I don't think the manufacturers are upset at all that one of the side effects of this trend has been to make aftermarket head unit installs a lot less convenient.

And I don't know any manufacturer that will sell you someone else's head unit as an aftermarket piece. It's up to you to find out how to take everything apart and fit something else in there on your own, or to find someone who knows—basically, jailbreaking your dashboard. Except you generally lose stuff (like steering wheel controls), while I hear jailbreaking is pretty painless these days.

Edit: Apple's app store isn't some third party stereo store, it's a store owned by the manufacturer itself. And car manufacturers are famous for having highly priced proprietary replacement parts, especially when it comes to electronics like stereos, if you aren't willing to deal with an outside store/brand. I really don't see any way Apple's less flexible with the iPhone than a car manufacturer is with their cars.

Agreed. I simply wanted to point out that the car manufacturer does not actively try to prevent the car owner or the installation shop from installing a stereo. However Apple does this with their devices. Everything must pass through Apple even after the sale is complete and the user owns the device, and that is just absurd. I can't imagine what older Macs that we used for audio applications would have been like if all software had to be approved by Apple. Apple does not have the expertise to write all that software. When I say Apple's strategy will backfire I mean that the more tightly they try to exercise control, the easier jailbreaking is going to get. The auto manufacturers may have made it very difficult to do stereo installations on newer models but they are not actively trying to interfere with stereo makers and installers after the car is sold. And why should they? The buyer made his choice when he bought the car whether he wanted any factory installed audio options or not. If after the sale the buyer wants to buy parts, or get service from an authorized dealer, she can do so. But the manufacturer does not try to interfere with her choice to get service (e.g. stereo installation) elsewhere. Imagine if every car stereo maker had to get approval from car manufacturers and could only sell their products in the manufacturer's distribution centers.