Because of our sinful nature, we'd never be able to please God. We need a miracle and God provides it for us in the new birth. The old nature goes away and God replaces it with a new one. Scripture says, those who believe and accept Him, are given the right to become His children. They're reborn, not with a physical birth, but one that comes from God. The new birth is a miracle, it's an act of God. Being a practitioner of religion, doesn't make you born again. Nothing could ever do this for you, but Him.