What is the importance of the new birth?

John 3:1-10

1 But there was a man of the Pharisees named Nicodemus, a ruler of the Jews; 2 who came to Jesus by night and said to him, “Rabbi, we know that you are a teacher come from God; for no one can do these miracles that you do, except God be with him .” 3 Jesus answered and said to him, “Truly, truly, I say to you, unless a man is born again, he cannot see the kingdom of God.” 4 Nicodemus said to him, “How can a man be born when he is old? Can he enter into his mother’s womb and be born?” 5 Jesus answered and said, “Truly, truly, I say to you, unless a man is born of water and the Spirit, he cannot enter into the kingdom of God. 6 That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. 7 Marvel not that I said to you, ‘You must be born again.’” 8 The wind blows where it wishes, and you hear the sound of it, but you do not know where it comes from and where it goes. So is everyone who is born of the Spirit. 9 Nicodemus said to him, How can these things be? 10 Jesus answered and said to him, You are a teacher of Israel, and you do not know these things?