All mobile devices use TCP/IP and have browsers. But they also all have specific add-ons: cases, plugs, add-on mics, tie-ins with devices - medical, etc. Just like all cars have a lot of after-market parts (spoilers, rims, etc) that all only fit specific car/models.
Kinda important to mention apps when talking about smartphones.
Sure, you can buy Angry Birds (or whatever) again for $0.99 if you switch platforms, but will you buy all of your apps again? And what if you really like an app that's only on one platform?
I am of the belief, that the latter is what we will prevent migration to a new platform but not the former.
Perhaps power users would rather not repurchase dozens of paids of apps; but for the average user, the amount of money invested into apps would probably be on par with the amount of money invested into a case for said phone.
