Brake Grinding Noise problems of the 2012 Cadillac CTS

Heard a grinding noise when brakes were applied, immediately took to dealership, was told brakes were completely gone, metal on metal. Asked why no warning brakes were going bad and why all four brakes needed to be replaced on so called high end/top quality vehicle like a Cadillac at only 30,000 miles and was told "because it hasn't been driven enough and brakes wore faster due to rust". Although the mechanics agreed this was an illogical explanation and seems like a product defect, I was still expected to pay $600-800 to replace the faulty parts - which I have not yet done. I was never provided an explanation for why there was absolutely no warning that the brakes were failing, even though I expressed my concern about this being a significant safety issue. After a quick google search, I discovered others have experienced premature brake wear on Cadillac vehicles.