I've thought of that. I'm currently running PR 2's, and they seem to have alot of life left in them, despite having quite a few miles on them.... So one reason is that my current tires have a good deal of life left in them. They have served me so well for commuting and daily use, that I'm not sure I would want to run anything else as a daily driver tire. Also I use my bike mostly for commuting in town and interstate travel, I dont go out and play in the "twisties" with her on the weekend often, so it seems a waste of a sticky tire.