When we are considering God, why did He create us, or when we need Divine Help, or what is Eternal Life, or is Heaven real? We are dealing with a dimension we do not know much about. That is why there are so many religions, each giving their interpretations.
God has to send someone who is from Heaven to tell us what Heaven is like and the correct reality of the Spirit, and about life after death.
God has decided that the only person who has the Authority to communicate to us about Him, is His Son.