Why GSP vs A. Silva Doesn't Make Sense for the Fighters

As much as I would love to see Anderson Silva vs Georges St. Pierre, I don't think it benefits either fighter. The welterweight division is stacked so GSP can fight credible challengers and go down in history as the most dominant welterweight of all time. Even though he'd be at a size disadvantage, if GSP loses it will lower his p4p status and his image of dominance which for a fighter is important. That's why GSP has some of the most mainstream sponsors of any MMA fighter, because he's a dominant athlete. If GSP won, although it will rocket his p4p status and image, I don’t think he can continually defend the middleweight title at his size. If Anderson loses it destroys his mystique and p4p ranking. Anderson's beating guys at 185 and 205 so what does fighting a welterweight, although a dominant one, benefit him?