Paul begins his letter to the Romans just as many letters begin, with an introduction. Introductions are important. They tell the audience who is speaking, where they come from and why they have authority or credibility - they help us understand why we should listen in the first place.
Matthew also gives us an introduction in his account of the birth of Jesus. His introduction explains and proclaims who this newborn babe is, this baby born to Mary and Joseph, and why we should pay attention to him.