Why are the rear brakes in my relatively new BMW 2 Series already worn?

I own an 18 month old BMW 2 Series Active Tourer which has just had it's first service at 17,100 miles. I'm told that the rear brake pads are worn and need replacing (£275). Having owned many cars, I've rarely had to replace rear pads and never before the front ones have been done. Is this something I should query further? Perhaps the setup is incorrect, resulting in premature brake wear. In this case, should it be a warranty issue?
Cars fitted with electromechanical parking brakes tend to wear their rear pads earlier. Also rusted rear discs wear the pads earlier. Rust accumulates on the rear discs because 90 per cent of a car's braking is at the front and if the car lightly brakes then the rear pads hardly touch the rear discs.
Answered by Honest John on

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