brake wear and noise

since i had the car there would be random brake noise, however i knew i had a issue the other day when i had already noticed it was time for the front brake pads to be changed but then noticed that my rear brake pads began grinding on the rotor metal to metal. How can the rear brakes wear faster then the front? Furthermore, how is it that no one has these brake pads for front and rear in stock. The ford dealer by my home had to special order both front and rear. The rear just got here and by the time they were put on the rotor on the passenger side was so badly chewed into that nobody would out it on the lathe so instead i had to buy a brand new passenger rotor for the rear. Now that is taken care of, i get a call from ford and they are telling me that the front brake pads are on back order and he has no idea when they will be in. This is ridiculous. For brake pads? I am about to go into ford and cancel the order for the front pads and get a refund. This is beginning to be a joke.