I was disappointed with the tire wear on Sukuta Girl's rear tire too. I replaced it somewhere around 7,000 miles, most of the wear was in the center from too many highway miles and not enough back roads
Tire wear patterns are discussed at length on many other boards (along with oil and oil filters) and most people seem to agree that tire wear on the left side is likely from riding on a lot of crown roads. Riders in other countries that ride on the other side of the road sometimes report seeing right side tire wear. And just to show you the wide range of beliefs out there, some people argue it's caused by engine torgue and a heavy hand on the throttle while others say it's just a predisposition by most riders to favor turning left (I believe most riders actually favor right turns).
There is also a small fringe element out there that brings up the side stand and attributes wear to the bike sitting still
-Terran Sin
Chief Farkle Mechanic and Proselytizer for Sukuta Girl