The skull is a wonderful bone that is designed to protect the most fragile organ in the human body, the brain. The shape of your skull is also a big part of determining your physical attractiveness to the human race. It is a big factor in facial structure, as the structure of it itself determines your face.
If one were to get stabbed in the head with a sharp object, the object must go through the skull in order to reach the brain. Without reaching the brain, then there would be permanent damage. It does have its limitations, as blunt force trauma can cause the brain to swell. A swollen brain is limited in the space to expand due to the brain.