Nothing is more personal than giving a person permission to inflict a permanent mark on the body whilst drawing blood causing pain in the process. All the elements of ritual are present in this very act from the marking of the body very often with sacred symbols, the drawing of blood (life-force) and inducing pain which is seen by many as something spiritual.
Before the advent of modern medicine many people believed that pain rather than being an inconvenience was something that brought the person closer to their God. They didn't attempt to mask the pain with painkillers but experienced it fully. Perhaps practices such as branding, suspension, amputations and other extreme body modifications are a reaction to the spiritual emptiness or 'pain' of modern day living.