I mentioned this in another thread, but...
With logic like this, let's remove all immobilizer chips, and for that matter, the need for keys in cars. I mean there are chop shops that will dismantle a car regardless of the fact that they are tracked via VIN and everything federally, right? What's the point of locking your door at night? I could just bash in your window, stick a gun to your head, and have my way with you.
No, nothing Apple does is going to thwart theft 100%. But the harder you make it for a thief, and the easier you make it for the rightful owner to render said phone unusable, the better off we all are. With what they have done on iOS 7, I could potential render my phone unusable within minutes after leaving my possession.
I don't know about you, but I know where my phone is at all times. It is almost a part of me. I might not feel a good thief lift it out of my pocket on the train, but it won't be long before I notice it's missing, certainly before the guy is able to sell it, because I am the guy who taps my pocker 1827648236872365 times a day to make sure my phone is still there. Again, it's not the same for everyone, but I would rather have some options than none.
Lastly, you are assuming that all iphone thieves are masterminds. I am sure there are some pretty decent thieves that have stolen good turned into money in hand minutes after the theft. Those are few and far between, especially if the loss of the phone isn;t even due to theft, but rather a legitimate loss (in my train example, slips out of pocket as I get off at my stop).