2010 Holden Cruze brake disc and pad wear

I just got my 2010 Holden Cruze serviced and they said it needed new front brake discs as they had worn beyond serviceable. It's only done 23,000 km and I don't drive the car hard or brake hard. I can understand the pads wearing, but I thought the discs should have lasted longer than that before needing replacement. What do you think?

Brakes, both pads and discs, are wearing out at a much faster rate than they once did, but that's very low mileage, so would be very skeptical of what I was being told. Check the discs yourself and have them justify their assertion that they not serviceable.