Many that claim to know the truth do not.
Our unrighteousness caused us to owe a sin debt to God. What did God require for that sin debt to be paid? You would need to be perfect, but you could not be. Only Christ lived a perfect life. His perfect life and unjust death was payment for your sin. That satisfied what God needed for justice to take place. Now, each one of us must personalize it to make it effective for us. That payment only applies to you if you place your faith in Him and His sacrificial death and then repent of your sins.
The rebirth is like having grant money made available to us. If we do not believe there is grant money that has been made available to us we will not ask for a grant because of our unbelief. Having that grant money available does not do us any good unless we act on it and claim it.
We must qualify for the grant however. We qualify when we give our lives to Christ and repent of our sins. Repentance means we turn around and head the other direction. It does not mean we are perfect. It means we are now heading in the other direction and on a road to becoming more Christ like. God accepts our repentance and belief in Christ in exchange for the righteousness of Christ, who was perfect.