Sure, they have identification chips. But who has a reader wand laying around? If your horse is stolen or gets lost, people may not have the means of transport to take it to someone who can check for a chip. Or there may not be a vet in town who can. Or, they might think 'finders keepers' and not bother to check at all!
Which is how I got to thinking...why not have a GPS or RFID chip implanted? In other words, a device that gives you the location and position of your horse?
If the animal, say, becomes lost or stolen, you could go online (some programs work with a cell phone). Put in your information, and locate the critter. I imagine this would be especially useful when high-priced horses are thieved from their stalls in the night. I believe it was a show jumper than vanished a few months ago (was later found).