It's because you're supposed to have more sense than the average four year old.
No artistic skill is needed to draw the tree or, in some cases, a house or a person. Draw a winter tree that's bare and you are likely an outgoing person although also one who is "easily influenced.
You should however learn the purpose and shape of different body parts.
Click the arrow and you will see the shapes in a drop down box. This helps because you're viewing the picture in a different way, and problem areas will stick out like a sore thumb.
