Xmas, actually the winter solstice, was celebrated for thousands of years before there was a Jesus.
There has always been a celebration when the shortest day passes and the world begins to move closer to Spring, summer and the food and warmth that comes with them.
In fact very few of the things that are associated with Xmas are Christian. Really only the nativity scene.
Trees were decorated by Pagans and wrapped gifts go back to the Druids.
The indoor tree comes from ancient Germanic beliefs and was only brought into the Christian world by Queen Victoria.
Even Santa Clause isn't originally Christian, also taken from ancient Germanic beliefs.
So, for a majority who have different beliefs or no religious beliefs, Jesus has never been the reason.