There is a difference though.
Car manufacturers tie you in to there brand for the love of the design, and maybe good service.
What Apple has done very succesfully is build an ecosystem that makes it difficult to leave.
Right from the start with itunes and DRM. You needed an ipod to play itunes music, no other mp3 players allowed.
Now with the iphones, etc... everything is built on that itunes core. Noone else is allowed in. Once you have enough investment into purchases via itunes, can you move?
You only effectively rent purchased items from itunes, you never own them. You cannot bequeath your itunes selection to your family should you die. (See Bruce Willis law suit against Apple).
The success with phones and ipods undeniably breathed life into the macs as well. You may also notice that itunes 10 introduced a pretty lethal bug for pc users of itunes. It basically ate the processing power from one core of a cpu. Any dual core users out there? well there you go your pc becomes sluggish becuase one core is being used for an idle itunes. nice huh. Then people buy a mac and go it works great. (I shout conspiracy

)
The rest of the mobile industry decided to use a consistent cable approach years ago. Micro USB. Not Apple, they went with their own proprietary connector. Ok I do understand why, you dont send audio down usb. Cleverly though this also locks out the hardware peripheral market.
Changing the connector is a risk, as now your old peripherals need an adaptor. Which removes one step of locking you in. But if you already have itunes I doubt you want to move to something else.
It creates a monopoly, albeit one that the purchaser buys into.
This isnt to say that others dont do this as well, Any Android users upgraded their phone recently? How quickly do all your contacts come across if they are synced with your gmail account? Shame facebook stopped playing with google though.
Or how about Amazon and the kindle. Although to be fair its a little bit easier to drop things on to the kindle, unlike having to jailbreak your apple device.