Tattoos have long been associated with rituals amongst tribal people. Young men would often be tattooed to mark their transition from boyhood to adulthood and to mark other rites of passage. The process of tattooing is deeply symbolic and contains many of the elements associated with ritual such as blood, symbolism and the awakening of the astral body through the experience of pain.
Tattoos and the modern practice of tattooing is seen by many as an almost mystical experience akin to the exchange of energy experienced during tantric sex or modern day sex magick. In many ways the level of trust involved in opening your body up to the tattooist is equivalent if not greater than the abandonment associated with the ecstasy and release of sex.
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.