The purpose of the sanctuary was to illustrate God's way, through Christ, of saving mankind. Remember, we're told that God's way "is in the sanctuary" Psalm 77:13. It is there that He separates sin from sinners so that sin can be destroyed while repentant sinners are saved, but one will not be sorry or repentant for sin unless they have some concept of what sin costs. How can that be conveyed? Put yourself back in time.
You have broken the law and are deserving of death, but being truly sorry for that sin, you follow God's instructions for getting rid of it. Leading a frolicking healthy lamb, you are on your way to the sanctuary, which is in the middle of the encampment.