The position of the Sun lamp has no effect on the way in which the image is rendered; Blender is only concerned with its angle. Why, then, are we moving the Sun lamps to these places in our scene? It may seem like extra work, but it serves more than a conceptual purpose. First, it gets us into the habit of moving our lamps around to where we imagine the source of light is coming from. Remember, some lamps do depend on the position of the lamp, such as the Spot lamp. Doing this habit with all the lamps puts us into the habit, so we don't confuse ourselves later.