I don't believe for a second that this benefits phone owners in any way. A thief is not going to sit there and do research on your phone model before he steals it. He's going to steal whatever he can and then figure out what to do with it.
Thieves don't do that research to specific models. Manufacturers don't like it if their competitors' models are easy to hawk on grey markets because that means their phones get stolen, too.
Thieves these days seem to really be struggling to even use them for parts, since these are also largely Apple DRMed, and are often resorting to threatening the previous owner to remove the activation lock remotely.
Of course theft often isn't preceded by a diligent cost-benefit analysis, but once there's a critical mass of unusable – even for parts – stolen phones, I believe it can make a difference.