Down Strokes

I've noticed that many players, particularly the youngsters, are having trouble with downstrokes. I don't understand the difficulty. Music has downbeat and upbeat and ussually corispond with down and upstrokes. When you strum down you have to bring the pick back up to strum down again so why not just run it right across the strings when you do. I know I'm oversimplifying a bit but the best answer is ussualy the simplest (Occman's Razor).
At any rate,If you are having trouble with it, don't be worried. Just get in there, laugh at the mistakes and once you loosen up and stop believing it's this mystical art you will do fine.

"Nobody paints by ear so why would I play guitar by sight?"