Modifying hardware on a desktop is much easier then on a phone. That the hardware is proprietary isn't nearly as big of a deal here. Its all embedded, can't really be upgraded anyway.

Using a different OS isn't that big of a deal either. PreOS won't run on it, Android won't fully support iPhone's features, and why should Apple waste resources making their OS run on hardware they don't support?

Now, if you wanted to complain about the App Store policies being bad, thats a valid complaint. But not proprietary hardware.