Michael Linton has also written another essay/post on not just which versions of Handel's Messiah one should buy and listen to but an essay dealing with why no other piece of music is so linked with Christmas as Handel's oratorio:
For musicians, Christmas means Messiah. This is not a comment upon musicians’ religiosity, but rather upon their finances. Messiah, Handel’s Messiah, is to America’s choral societies and orchestras what La Bohème is to its opera houses and Nutcracker to its ballets: the guaranteed full house that can bankroll a whole season of deficits. Between Thanksgiving and New Year’s, Handel’s oratorio receives hundreds of performances, from church choirs with organ accompaniment to major symphonies with their professional choruses.
[...] While Messiah is a masterpiece, it is but one of many from Handel’s pen, masterpieces that have not endured so steadfastly as Messiah. Why?
I think the answer lies in the fact that for the last two hundred years, English-speaking Christianity, and in particular, American Christianity, has found a singularly eloquent vehicle for self-reflection in Messiah. Despite much talk to the contrary, religion remains deeply important to most Americans. But as many writers have noted, that religiosity is not denominational or even confessional in nature. Instead, it is individualistic, a matter of personal belief and individual choice not dictated by bishops, mediated by ritual, or regulated by the state. Furthermore, American Christianity is deeply eschatological, the sense of the impending eschaton being not so much a dread premonition of a coming doom, but rather a purposeful optimism. Americans work for and expect the eventual establishment of the kingdom of God, that "city on a hill."
Messiah speaks to such a Christianity. Although reminiscent of the lectionary texts from Advent through Trinity from the Book of Common Prayer, the oratorio cannot be said to be denominational (although the lack of passages dealing with Mary certainly gives it a distinctly Protestant cast). Its biblical texts are equally accessible to Episcopalians and National Baptists, Methodists and Pentecostals, and until fairly recently, could be said to be known by heart by almost all. Unlike Bach’s cantatas and passions, the oratorio requires neither a liturgical setting nor a particular occasion for it to be grasped. And despite the current custom of abridged Christmas performances (an aberration largely the result of reduced attention spans), the oratorio is not seasonal. If the work points to anything at all, it is neither Christmas nor Easter but rather the Second Coming and the individual’s faith in Christ’s eventual triumph.
Messiah is a concert work for the concert hall, and very much in the mold of the modern Protestant sermon, which entertains its listener for the purpose of edifying him. Like his contemporary George Whitefield (who was also criticized for using theatrical devices for religious ends), Handel uses the conventions of the theater to compel his listener into a personal encounter with the scriptural texts. Messiah, contrary to most critics’ readings, is highly dramatic. But its drama is an interior one, a personal confrontation between the individual listener and the story of salvation that Handel unfolds before him. To a population where that confrontation is the fulcrum of their lives, performances of Messiah become almost autobiographical.
It is because of the religious character of Americans that Messiah is so important here. And because of that religious character, it can be said that Messiah forms the foundation of America’s art music culture. Not only do performances of the oratorio undergird the finances of many of the country’s performing organizations, the work itself is the entrance of tens of thousands into the realm of classical music. It is not only the one classical piece that almost everyone will recognize (hence Madison Avenue’s shameless exploitation of it), but in many cases it is the only major classical piece that most amateur musicians will themselves perform. My own case is not unusual. Messiah was the first piece of classical music I heard live, the first one I performed as an amateur singer, and the first one I conducted as a professional musician.