We never took Parts from a grave yard or dug up graves. Today Many witches will bring out a ceramic skull for certain rites to represent there ancestors. Old Trads have a lot of tools that may seem strange to you. Each have a need or we would not use them. There where Dark Witches on the other hands who would practice the dark arts of necromancy and would go mad for it.
Sprits are much like people.
We will have insane people no matter what day and age it is. View the skull as this. We all have one it is a respectful way to remember our ancestors. It is the home of the mind set and where all knowledge comes from. We never use a skull we don't know and it is always have permission.