Being an historical Jesus 'Lao Shih' (Chinese for 'Long Time Student' or 'professor') the ancient and deeply traditional Winter Solstice Celebration (captured by the various religions and cultural concerns as "Christmas," "Chanukah," and "Kwanzaa" here in the Ooooh Esssss of Aye) is a fine time as an historical Jesus student to examine the fictional tales about the birth of Jesus of Nazareth as found in the Gospels of Matthew and Luke. Neither of the tales, of course, is historical. They conflict with each other as well as with other contemporary documentation and events sufficiently enough to make it clear that their authors, whether the evangelist/redactors themselves, or someone previous to them both who created the tales (I tend to think the evangelists were the ones who came up with the stories) made up these stories in the good old Jewish manner of creating fictional tales to make points. Not really being history (Jesus was most likely born of Joseph and Mary in Nazareth, Mary being the wife or fiance of Joseph at the time Joseph got her pregnant), one can forget about that and look at what the stories are really after and why the creators of them said what they did.
Matthew, of course, wanted to present his Master as a combination New Moses (other babes killed but not him), Once and future Davidic King (Being born in Bethlehem and of a Virgin [a mistaken Greek translation of the original Hebrew 'Almah'-young woman capable of being married]), and the Ideal Israelite (coming out of Egypt like Israel as 'son' of Yahweh, the Jewish god). That's why Matthew's story is written as it is.
Luke wanted to present Jesus as John's Master when the situation was really the other way around historically, as well as the Once and future Ideal Davidic King (Bethlehem Birth of a Virgin), divinely appointed (angels singing to shepherds, etc.).
None of the above ever happened. Both tales are fictional as far as the evidence is concerned. But the real question is why the evangelists made up these stories. And that can only be because of the high value they placed upon Jesus's teachings and particularly on the hope he held out for the future to those who, in terms of society at the time, were the folks rather much at the bottom of the barrel: the poor, the maimed, the sick, the peasantry: those put upon by the rich, the privileged, and the powerful. Jesus was the 'upside down' man whose life and commitments aimed at proclaiming a certain-to-come better world that the underdogs of the age could only dream about. That message still has validity and force today, even if the mythology that came to surround it and him has long since been proved irrelevant and unreal. There may be no god to destroy and remake the universe who is about to upend things almost immediately as Jesus and his Mentor, John the Baptist, thought before him, but his message challenges well-off humanity itself to give up its hubris and see clearly the necessity to care for others. That's still powerful stuff--as powerful as the ancient notion behind the Winter Solstice Celebrations down the many millenia among humans that saw the cold days diminishing, and the warmth of the sun lengthening the light again toward Spring even amidst the sometime frigidness of present days. That message remains more real, regnant, and meaningful than the fictitious mythology in which it comes so nicely dressed!