Although I share your concerns about the ease at which stolen iPhones can be activated, I don't think it's part of a larger conspiracy for Apple and AT&T to make more money.
IMEI's can be blocked on a cellular network. However, AT&T has to have a police report in order to block the IMEI. I would suggest calling 611 back and asking them what the procedures are for getting that IMEI blocked from the network. It CAN be done with a police report.
That said I do agree it's B.S. that anyone has to go through that. You'd think they'd block IMEI's with a single phone call from the customer simply to cut down on insurance fraud.
The cellular provider's requirement for a police report is actually a smart idea and it is there to protect the customers. Think about how much security is actually required to make changes on an account, really very little. With AT&T they generally ask you to verify the last 4 of your social security number. That's it unless you have password protected your account.
Now imagine that ex-girlfriend you just broke up with, you know the one that lived with you and had access to all of your records, the one that is PO'd because she came home and caught you in bed with another woman. Now imagine she is so PO'd she gets her brother to call the cell phone company claiming he is you and he tells them to suspend your account and that your iPhone was stolen and because she had access to your personal information, he can verify the the last 4 of your social security number. So because the cellular provider didn't require the police report, they lock your imei and lock your account blocking any usage.
That's an ugly situation but one that happens more often than you might think. And trust me, once the provider takes this action based on the claim of theft the trouble you will have to go through to get it fixed is much greater than you might suspect.