Actually, with a police report (especially if it's a tracked batch nicked on it's way to a reseller and insurance companies are paying out), they will make a note that the device is stolen and police will be informed if it's ever presented for repair, etc. Apple don't maintain a blacklist and won't stop a phone being activated (that's down to the carriers), but a phone can be marked as "deny service", which cannot be overridden by Store staff or AppleCare.
I once had someone come in with an iPod which they'd bought "from a local shop" (as always). When I typed the serial number into MG it came up with a message stating that the device was stolen, to keep hold of the device, deny service and to contact the authorities. Turns out it was a display model that was stolen from our store a few weeks beforehand.
You'll be surprised at how much information is available about a device to store staff. They can see the first activated network, the current activated network, lock status, when it was first activated, when it was first purchased (Apple-bought) or when it was shipped to a retailer (auth resellers). They can even see which shop it was sent to, and in which town/city (e.g. it will show that the phone was shipped to the Apple Store, Brighton, on 01/01/2016, sold (shipped to, if a reseller) on 05/01/2016 and activated on EE on 06/01/2016).
For an Apple-sold device, a phone with a ship-date and activation date with no POS date will ring alarm bells. That and the "service denied" message which cannot be overridden if a device is marked as such. You'd be surprised how cheeky thieves can be. Before the days of activation lock, after an influx of stolen phones which "would not power on" and always "bought from eBay or a local shop", we actually had a process for testing suspicious phones who's names didn't match the person at the appointment and "didn't power on", using a multimeter, to see if they'd been microwaved.