Because it is an announcement:
if I had something good and keep it to myself, the good thing remains with me. The gospel is not the gospel without an announcement. Luke 1:19 "I am Gabriel," the angel answered. "I stand in the presence of God, who sent me to speak to you and tell you this good news. This angel came with good news that Mary was to be with child and this child is to be the savior of the human race.The announcement has got something to do with you:
If someone came with good news and told you that he actually carries with him good news and such news has got nothing to do with you, the excitement levels will drop but if the news has got something to do with you, and something at would change your world completely, it would suddenly change your countenance and will warm your heart and depending with the intensity of the news, in ways that you cannot fathom. The announcement has something to do with the whole world. The news is that Mary was to carry within her the savior of the world. The gospel is a universal message. Jesus is the remedy for the sins not ours only but also of the whole world (1 john 2:2) We owe it to Jesus that the course of history has changed for the whole world. He came not be served but to serve and to give his life as a ransom for many.The announcement changes the whole course of history.
The child is to become the savior of the whole human race. He is the Wonderful counselor, mighty God everlasting father, prince of peace.
