Each time you use the brakes, the energy has to be dissipated somehow, and that is done by heating up the brake pads and rotors. I know people that will use brakes the entire way down a mountain, even in a stick shift but even more so in an automatic... and then wonder why it smells like overheating brakes and why their rotors are glowing red.
Then comes the weird feeling while braking because the rotors are warped...