It was necessary for Jesus to be born of virgin for the sake of his sinless nature. He did not have a biological earthly father so he did not inherit a sin nature, rather he was the Son of God. It proved he had a heavenly origin and that he existed eternally. It was also important for salvation. Without a perfect, sinless, sacrifice there could be no salvation. Jesus was that perfect sacrifice because he lived a sinless life from the moment of conception. It also made Christ unique. No one else has ever been born in this manner. From the beginning to the end Jesus’ life was a miracle.