brakes question

[chaabraham]

okay so recently when I drive around and start braking, the driver side brakes sound like they are grating against the rotor....so I checked the brake pad and its pretty worn out prob less than 10%percent.....so i thought why not check the others, but surprisingly the other brake pads where in good health, at least 50% left. I was wondering why only one pad is more worn than the others ?? O.o

[mazda3UR]

Hanging caliper. Need to pull it off, clean it up and lube the slides