Traditionally, Christians marked December as the season of Advent, paralleling the role of Lent before Easter. Christmas celebrations were to begin at Christmas. That practice has been under siege for generations, with Christmas, it seems, now threatening to engulf Thanksgiving.
Clergy often attribute the fading of Advent to a consumer economy’s disregard for the disciplines of the church year, but a little digging suggests more is involved. Holidays that don’t have associated foods and decorations tend to be marginalized. Compare Advent and Pentecost, or in the secular world, Labor Day, with Christmas, Easter and Halloween. Non-Jews often wrongly assume that Hanukkah is the main Jewish holiday because it is so heavily marketed.
This is more than just rampant consumerism, however, since stores could just as easily market Christmas through January as through December. What we see in December is a clash of calendars. In the church year, seasons begin with the holiday in question: Christmas Day starts the season of the same name. American popular culture is exactly the reverse: the holiday ends the period of celebration. Once a given holiday, religious or secular, is over, the decorations come down, and the special foods go on sale.
For modern Americans, preparation and celebration are intertwined rather than separate activities. Therefore, the days between Christmas and New Year's comprise a quiet, even solemn, period of exhaustion, not the apex of celebration. Instead of a continuation of Christmas or New Year’s, January 2 will mark the start... of Valentine’s Day.