And this is different than say cell phone providers or cell phone software vendors? Google, RIM and MS would rather you buy a new device with the latest software than have to support some older version of the software I am sure.
Last I checked the vast majority of phones don't have their prices measured in the thousands of dollars for used models and in the tens of thousands for new models even without a contract subsidy.
I dislike the phone lock-in model as much as most people, but we are talking a slightly different scale here. Hell, most of these integrated head units alone cost more than vast majority of unsubsidized phones.
Case in point, Audi's MMI is over 3K to upgrade from an already fancy screen to manage car and entertainment.