It is a simple heuristic that in bad whether it is easier to run the ball, play defense, don't turn the ball over and have a good kicking game. If you have a HOF like Jim Kelly or the guys you mentioned you can do more. Ideally your team can do it all, because you play on the road right. But, if you don't have a great thrower, it doesn't make sense to come out throwing the ball all over the place in bad weather. Ever see Dan Fouts in the 1982 championship game? Not pretty!