Originally Posted by Hopper
If you aren't in the air, you are pedaling or turning.
Not really. if WE (ie, us here in Adelaide) arent in the air we are pedalling or turning but not everyone. Its just that the Adelaide tracks arent exactly 'super steep'. On some tracks, even the pro's coast because they don't have the gearing or they simply dont need to.
But in a answer to the question, you need the gears for different steepnesses of tracks and for the odd uphill pedal. And like Hopper said, Downhillers pedal a lot more than you think.