1. Animism - reincarnation is the unending circulation and transformation of a finite number of immortal souls through multiple sentient entities - this circulation and transformation is 'life' itself.
2. Eastern Hinduism/ Buddhism/ Jainism - reincarnation is the purpose of life: reincarnation is a punishment. Life is suffering, but death is not an escape unless or until multiple lives have educated the soul to die and escape reincarnation, when individual self-hood is extinguished and reabsorbed into the primary energies.
3. Modern New Age-ism - reincarnation is the purpose of life: reincarnation is an ascent towards divinity; necessary because one life is not enough to accomplish all the learning and spiritual progression needed to bridge between the human and the divine.
Christians, I take it, believe that reincarnation simply does not happen, at least not as a norm; although I don't think Christians would regard reincarnation as absolutely impossible, if it was necessary in some way to God's purposes - which means it might have happened, but exceptionally and not as a standard part of God's basic plan of salvation.