Reporting a phone stolen adds its hardware identifier to a shared database that carriers consult. Understanding what that block does, and does not, do explains why theft persists.
The identifier is separate from the account
Every cellular device carries a permanent equipment identifier distinct from the subscriber identity on the SIM. Changing the SIM does not change it.
Carriers check that identifier when a device attaches, which allows a specific handset to be refused service regardless of which account is used.
The identifier is burned into the device at manufacture, and altering it is both technically difficult and illegal in the United States.
A shared registry makes the block portable
Blocking on one network alone would simply move a stolen device to another. US carriers therefore contribute to and query a common blocklist.
Once listed, the device is refused activation across participating networks, which removes most of its domestic resale value.
Coverage is not global. Networks in other countries may not consult the same registry, which is why stolen devices are frequently exported.
Blocking service is not disabling the device
A blocked phone still powers on and still works on Wi-Fi. It can be used as a media player, a camera or a development device.
Its parts also retain value. Displays, cameras and enclosures are harvested and sold into the repair supply chain regardless of the block.
This is why theft continues despite the registry. The block reduces the value of the whole device without eliminating the value of its components.
Activation locks do the work the block cannot
Manufacturer account locks tie the device to its owner's credentials at a level below the operating system, so a wipe does not clear them.
A locked device cannot be set up by a new user, which removes its usefulness even offline. That is a stronger deterrent than a service block.
It also creates a secondary problem: legitimately acquired used devices with an unremoved lock are effectively unusable, and no reseller can clear them.
Reporting order matters more than people expect
The registry entry is created by the carrier report, while the account lock is set by the manufacturer's service. They are separate systems requiring separate actions.
Remote-erase commands queue until the device connects, so a wipe issued after a thief has kept the device offline may never execute.
Marking a device lost rather than wiping it preserves the lock and its tracking, which is generally more useful than an erase that removes the association.