Luke 5:32

I have not come to call the righteous, but sinners to repentance.  

What is the purpose of sin? Sins’ goal is to create a division between God and us.  Sin leads us down a path that is a dead end.  When we are lost, we need that voice of God to call us back.  A sinner repents because the error is revealed.  Most people sin because they lack knowledge from God of how to do better.