All those three-point turns. With each turn of the steering wheel, pressure is bought to bear on the front tires. Resistance causes friction, which in turn produces heat. The front tires wear quicker than the rears. There's a good reason for this.
Tires develop wear patterns as they age.
Some of these patterns are tied to the suspension system and the alignment. That's why we keep the tires on the same side of the car. One more thing. Refer to your owner's manual for exact guidelines, but most manufacturers recommend rotating tires roughly every 5,000 to 10,000 miles. Again, see your owner's manual for specifics.