I wondered the same thing about the 17" rear. When I was shopping 18" rears for my G650X, there was a myriad of DOT dirt tires and for the most part they were cheap. I ended up putting the MEFO Super Explorer on a couple thousand miles before I sold it and I LOVED THAT TIRE. So when I got my 8gs I went right back to MEFO and they don't make that tire in a 17". Ended up with the Heidenau which is OK, but the Super Explorer looked great on the bike, looked aggressive but had great road manner and would hook up in anything. It seems that DS tires in the 17" are mostly street tires with a few exceptions. Yes, I know the Conti looks great, but if I'm going to spend that much on a tire, I want it to last more than 4K.
Somebody's gonna have to go back and get a shitload of dimes.