Why does God want/require sacrifice in the first place?

Sin must be punished or paid for. If you commit a crime today you have to pay the price. In order for the sinner to once again have fellowship with God they must have their sins dealt with. God sent His Son to pay for the sins of the world. Anyone who believes on His Son whom He sent will have forgiveness of their sins and inherit eternal life. God will not have sin in His presence therefor one must have their sins forgiven by Christ in order to be able to go to heaven when you die. This is the main theme of the bible. The Old testament prophesied the coming of the Messiah (Christ) and the New testament tells of His coming and how we can inherit eternal life with Him. This is the ONLY way to heaven according to the word of God.