They are born great and divine. The Roman Emperor, after all, claimed to be a god himself, as did the Pharaoh and other mighty rulers. When we know these details about life in the ancient world, a number of things about Christmas become more understandable. First of all, we understand the scholars' debate about the actual birth date of Jesus Christ. He wasn't born famous or an emperor, so it is extremely difficult by secular historical standards to find any proof for this particular day or that, especially since the Jewish and the pagan calendars don't match up easily.
Secular historians are also uncomfortable with dating an event on the basis of divine miracles.
Second of all, we understand why early Christians paid much more attention to Good Friday and Easter. Without the cross of redemption or the resurrection from the dead that promises us an eternal life by the grace of God, Christmas would be nothing more than a typical pagan winter or children's festival. Third of all, we understand why the celebration of Christmas, on whatever date, did not become general and public until the fourth century, when Christianity became a legal, rather than a persecuted, religion. Prior to this, a great festival to honor Christ's birth could easily have been seen as an act of civil insurrection, denying the divinity of Caesar and his gods. To celebrate Christmas is to say in the most public way possible that when Jesus Christ is born, he is already the Lord of lords, the King of kings, and God made flesh.