Its a good excuse to be able to eat drink and be merry with family and friends and have a good time associating with those you love and those that love you .
And let`s not forget the kids ,what a joyous time it is for them and the parents want them to have a special time.
Nothing religious about it at all.
I would hazard a guess that a great proportion of people in western lands and maybe also elsewhere that Xmas is celebrated by the majority of people who do not practice any Christian religion .
And that those who do attend a Church service at Xmas probably only do so on those other occasions such as Easter ,Weddings and funerals. If that.