Laura Hancock - Pilgrimage

Why is pilgrimage important? Why is it an integral part to so many religions and peoples? Pilgrimage is a liminal experience that allows for a 'cleansing' of the mind and soul. It fosters communitas, and the instinct for survival. How does pilgrimage change a person for the long run though? How does this liminal experience change stay with a person after leaving this social anti-structure?