The answer is simple - the slider pins are not moving freely on the side that is worn. The accordion boot may be torn and allow water into the opening nad cause it to rust. Pretty common. Caliper needs to be unbolted, pins removed, clean pins and holes of rust and old lube - relube with high-temp silocone lube (like Sly-Glide) reassemble with good dust boots. Repair kits are available.

The reason it happened is that when the brake is released and the piston and inner pad retracts, friction in the pins does not allow the caliper and outer shoe to move outward and away from the rotor. Slider hardware is ALWAYS the first thing to look at when the outer pad is worn more than the inner...this is just as true on a Chevy.