It was only a short while before that BMW became the first to introduce the special device that only Dealers had, to turn off the service light so that they could have a monopoly on BMW servicing if you wanted to part ex your s/h BMW for a new one at the dealers as it had to be proven to be serviced by them throughout it's life!
Mind you it wasn't long before local motor factors started hiring out the service device key to turn off the service light, the idea was for when independant garages serviced the cars, but shortly after that dodgy car salesmen would just hire the device, turn the service light out and not bother with the service, so saving themselves more money.