Answer: Mysticism
The main reason of all Hinduism aspects is Mysticism, which means contact with the absolute within the living body. This absolute can be understood in any form, from the personal god of dualism, to absolute Brahman of Aduaita (the ultimate, transcendent and immanent God of the latter Vedas), in other words, is a contact with this higher truth.
In Hinduism, the goal of religion is only this contact with the truth, and until this is achieved the spiritual quest is incomplete. All other things are consider secondary and no performance of religious duties can be a substitute. Vedanta says that is not a matter of experiencing but of knowing. This is because no experience can be irrefutable about anything.