If we were created by God, why are we so complex?

The complexity of processes such as the clotting of blood and respiration can be explained by evolution. Small and gradual changes improved the systems in many ways, making it complex. If there is an all knowing creator God, why didn't it just make our bodily processes simple, meaning there is less chance for them to go wrong? A man making a watch does not put extra parts in to get the same function. Is God just showing off?