sounds crazy, but hear me out. the human leg naturally bends forward at the knee, so when the human leg is covered by a soft, moveable garment layer, the natural tendency of the soft movable garment is to move with the leg, moreso as a bend, you guessed it, at the knee!
this is the part that's going to blow your mind.
when you're skiing, the natural skiers stance due to the shape of the ski boot is to bend forward, that's right! at the knee! so it would only make sense that your snow pants, that you wear when skiing, would have a natural forward bend at the knee to accommodate a human legs natural range of movement.
hope this helps!!!!!