I once heard a beautiful explanation for burial from one of my teachers. Discussing the story of when Avraham buried his wife, my teacher showed how Avraham repeatedly described the burial site, and insisted on paying Efron the Hittite, although Efron offered it for free.
Why did Avraham want to pay for that which was free? Why did he keep repeating the description of the site?
The rabbi explained that Avraham had the true concept of burial: It is not the removal of the corpse, conversely, it is actually the initiation of the other part of man's existence. Life after death is a positive state. It is the higher state as well.
Merely burying Sarah would not demonstrate that Sarah's continued existence was a reality. This is why Avraham insisted on paying for the grave site. He wanted a positive acquisition to demonstrate a positive state that Sarah was now experiencing.
Additionally, we bury a corpse immediately so as to demonstrate that the body is not man's essence. Just the opposite of what other religions do, as they keep the body around for a wake. The other religions feel that the body is everything. As Jews we recognize that the body is only the means of interaction for the soul on this Earth. But once the soul departs, we must demonstrate that this person's true existence is no longer tied to this body, and we therefore bury it right away.