God choose the unique way through a Virgin to reveal Himself because if He was to be born by a woman who was not a virgin it would have been taken as any other human birth of a human baby but in this case it had to be unique because the ways of God are mysterious no one can be able to understand fully.God in a way also honours virginity and purity of heart that is why Mary's virginity and purity of heart was honoured.She became the temple of God and the power of the Most high came to her.