It just doesn't matter as much if they don't make first downs. Clearly going 3 and out kills your defense but you're dismissing all the other opportunities for rest. What about 2 first downs and then a punt? That could be anywhere from say 2-4.5 minutes. Ask anyone who's ever boxed, wrestled, or played on the line in football, that kind of rest can be crucial. We're not ready to run plays that fast. In theory it sounds simply wonderful with the problems we have on offense it sounds stubborn.