It's my understanding that phones have a limited life outside your hands -- thief doesn't get the charger, you report the phone stolen and the SIM card is deactivated, boom. Done. And if you're smart you already had a lock on your phone and/or encryption, so it's not like they're going to get your personal info either. Why do we need a way to remotely deactivate cell phones?
The thief sells your phone to someone who will ship it to another country, wipe it to factory defaults, and sell it on the black market - possibly repackaged as new, if it's in good enough condition.
You said the thief doesn't get the charger, but I can buy an iPhone 4 USB cable for about $6 retail, which means the wholesale price is closer to $2, and I'm sure they can be obtained for less. The new iPhone 5 ones are probably a little more just because they're new. I expect many other phones use Micro USB, since that's the official standard in Europe, and obviously those are dirt cheap.
An international stolen device registry would prevent these stolen phones from operating, which means people will stop buying them, which means the market will dry up, which means people will stop stealing them because they no longer have value. It won't happen overnight, but if everyone's on board, it will help a lot.