Why the U.S. Doesn't care about blacklisting...
Here in the U.S, if you lose your phone you go into the carrier's shop, get a new phone, and the old phone is disconnected from the network (when the new phone is activated, the old one is deactivated). So, why bother blacklisting it? Nobody cares.
The phones themselves are usually very cheap, as Eddie pointed out above. We get 'em for free with our plans, so who cares?
And as Wonderkid mentioned, there isn't as much casual "nicking" of phones in the U.S. because we're basically nuts and thrive on violence and chaos. I'm consistently astonished at the weird stuff "chavs" get away with over in England -- take "happy slapping" for instance, where teenagers run up to strangers and smack them in the head. But nobody attacks them! The victim just pouts!
If someone was to try that here in New York, they'd be beaten to within an inch of their lives. They might not even be able to flee, because a sufficiently pissed off New Yorker would throw a garbage can lid at 'em like a giant frisbee. GOD forbid you try happy slapping somewhere like Texas or Arizona... Everyone's packing heat down there, you'll get shot! At least New Yorkers -- USUALLY -- won't kill you!
I'm reminded of the story of a guy who tried to mug an old granny in the parking lot of a supermarket. He told her to give him her purse; she swung it at his head. He was knocked cold, and when the cops showed up, It turned out the old granny had kept two giant bricks in there! The mugger woke up in the ICU with a handcuff tying him to his bed and a massive concussion. The granny was treated like a hero in the newspaper the next day. I doubt that'd happen in England; your grannies are WAY too mannerly to go around bricking people in the head.
We Americans are pretty docile most of the time, but if you give us an excuse to go berserk, we won't put it to waste! :)