By placing lines at various distances from one another, the image gets more structure and gives the illusion of a body. A variation in width gives more dimension to the image and illustrates a sense of realism.
I love the first poster for this movie "You Will Meet a Tall Dark Stranger" the latest woody allen film. The negative space created with the hands is beautiful. Here is the feature film trailer for the movie "You Will Meet a Tall Dark Stranger"