Hanging the foot out on MotoGP does a couple of things. One is for stability, you'll see a lot of times when the riders come in to that corner, the back wheel is off the ground. The back wheels is what usually stabilises a bike, if its off the ground it can't do that, so they hang their foot out like a cat's tail. The other reasons are lower COG before they're leaned over and also increased wind resistance, because every advantage they can get to decelerate they'll take, since every millisecond counts.