Every part that comes off your car goes into a box with your registration written on the side, and the box is on the office counter when you come to pay.
We do not do this because customers ask. Almost nobody asks, and that is exactly why it is worth doing: a garage that hands back the old pads every time is a garage that cannot quietly charge for pads it did not fit.
Look at them or do not look at them. Plenty of people glance in the box and leave it with us, which is fine, and we dispose of the oil and the filters properly.
The one thing we will always get out and show you is a brake pad, because once you have seen a worn pad beside a new one you never again need to be persuaded about brakes.