Most people in the western world are Christians in name only and if they attend a church service at all it is only for weddings births Easter or someones funeral or their own
The rest that celebrate xmas are people that never attend a church service ever.It has become a secular celebration in so called Christian nations by people that are not religious at all.
Its an excuse for a celebration food drink and partys
I know , me and my extended family are non religious and we enjoy getting together in celebration.