Often it is argued that "Jesus is the reason for the season" as a way to ensure a specific way of understanding Christmas is upheld. But the fact of the matter is that Jesus is not the reason for the Christmas season.
The reason we celebrate Christmas day is because there are other days when tragedy happens.
The reason God came to humanity in the form of Christ at Christmas is because of darkness among humans. The reason for the season of Christmas is the darkness of humankind.
Jesus is the response, not the reason.
Think of it like going to the doctor. The reason we go to the doctor is because of an ailment or sickness. We do not go to the doctor because the doctor has access to treatment. The treatment is the response of the doctor to the reason you are there - a sickness.
The more we focus on the light (Jesus) we do not see how much darkness there is... And, even more than that, we live in the dark much of the time.
The reason for Christmas is because of darkness. Jesus would not have been sent if we lived in the light.