[sarettah]

All this, of course, is just one manifestation of a more general problem with having Christmas Day as a national holiday in a country where there are all sorts of religious beliefs, including none, and where the First Amendment to the Constitution declares that "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof."

Christmas is a national holiday partly because it is a major religious holiday of the country's dominant religion, but that certainly can't be the whole story, because Easter, which is arguably a more important religious holiday, is not a national holiday. You don't have to look far to find the rest of the story. Christmas became a national holiday because it involved the exchange of gifts, which is now by far the biggest part of the celebration. Take a holiday of the dominant religion, add gift exchange as a major part of the celebration, and---presto!---the modern market economy responds to deliver the gifts and to pump up demand for even more gifts year after year. Anybody, whether or not they attribute any religious significance to Christmas, can participate in the gift exchange, and the consumer economy not only encourages them to do so, it really requires them to participate, for Christmas has become the great engine of the consumer economy.

http://info.phys.unm.edu/~caves/commentary/012.html