Have you ever known them to work? If not who is to say they all failed the same day, just that they failed before you owned the car.
My D4 (approved used) didn't have puddle illumination on the handles - or so I thought, until I realised that all four LEDs had failed! Easy fix in my case, 4 new "LEDs" at about £50 all in
Bear in mind, all of the parts fitted at the factory will be from the same batch - so it stands to reason may fail around the same time - especially when it comes to things like motors?