Breaking the symmetry
Among the 12 basic principles stated by the animation legends Frank Thomas and Ollie Johnston, there is one called Solid Drawing. Even if you can't draw anything else other than a stick figure, this principle remains as important for those who use the computer as is does for classical 2D animators.
Think of the computer and its software as a highly sophisticated and expensive kind of pencil. A pencil doesn't make a masterpiece for itself, nor the computer. It's the person behind the tool who makes the difference.
When posing your character on the screen you're creating a "drawing", even if there's no pencil and paper involved. Thus, you have to take control of the shapes presented on the screen to make this drawing more appealing to the audience and tell a story.
Images rendered in a 3D application tend to look too perfect and symmetrical, and that does not feel natural. A big part of the work of artists involved in the processes of modeling, texturing, and lighting is...