Matt,

 

I assume you also had the same number of takeoffs.  If your home airport has a prevailing crosswind and runway crown, perhaps it sees as much wear on the takeoff.  If the prevailing x-wind is from the left, that may provide even more work on one tire than on the other.

 

I have about 180 TOs and landings over 18 mos. and am about to change tires because of a flat spot on the left (oops) and "baldness" on the right.  In the summer (more flying than the winter when winds are from the NW), most operations are from runway 27 with winds out of the SW - yes, I must do a bit of brake tapping during the initial takeoff run and landing roll out.