M.D. Goulder, in a series of well-worth-reading books, proposed a controversial account of how the Synoptic Gospels got their final form: as liturgical pericopae for the Jewish Torah lectionary system. By no means is his argument air-tight, but it is well worth considering. From the book of Acts, it seems clear that various Jewish holy days were still important to early Christians, if not binding upon Gentile converts. However, the liturgical year would still have been in place and attractive to these amalgams of Jewish and Gentile worshipers. So much so that "Quartodecimanism" (or celebrating Easter always on the 14th of Nisan, as Jews start Passover) controversy created major splits in the early Christian community -- possibly because it would be easy for many converts to return to the communities that they originally hailed from (Rodney Stark argues this point, in The Rise of Christianity, for Chrysostom's invective against Jews in his time). Later, of course, the standard Church year would arise, not celebrating festivals of Passover, Tabernacles, and the like, but instead Easter, Christmas, Lent, and Pentecost (not, notably, in that order). Being from a staunch Scottish Presbyterian background which holds to the so-called "Regulative Principle of Worship", I knew little about this or its historical background. My own study has led me to the conclusion that not only is the Church year a good thing in its own right, but that a return and reformulating of the traditional lections are greatly needed in the Church today.
If Goulder is right (and I think, with certain modifications and provisios, that he is), then the key to understanding why some of the NT books are the way they are, and the key to the Synoptic problem lies not with "Q" or some such mythological construct of the scholars, but rather within the life and activity of the Church. The Bible is, was, and always shall be the Book of the Church (which is why, not incidentally, the text of the book is important, but I've already argued for the Byzantine text tradition elsewhere). This Book, read properly -- that is, liturgically -- opens up vistas of interpretation for the common man, not just the cloistered clergy or lofty academic. The Book of the Church becomes the Book of the Community of God.
Ordered lections guard the people of God, as well, from well-meaning ministers who always face the threat of Marcionism. Many churches rarely, if ever, read from God's Torah or the Prophets. Many concentrate either on Paul or the Gospels, to the neglect of other parts of Scripture the interpret these things properly. A lop-sided view of the faith, or a fear of the Torah, or some such thing often arises ("we're New Testament Christians"...whatever that means!). Having lections requires the discipline of reading through the Bible once a year (this is assuming daily lections, but I've also heard of three year or even monthly patterns of lections), leaving nothing out as "unseemly" or "not Gospel" (as if any word from God was not a reflection and expression of the Word of God -- no part of Scripture is mere "straw"!). Lections force us to confront what we do not wish to confront in Scripture, that it is not a book of religious niceties, but God's story about His redemption of the world through His Son (Israel as type, Jesus as fulfillment), even in the messy bits of human life. We do not, understandably, want to be confronted in worship by the Levite's concubine, or even the atrocity of the Crucifixion, but we must be: the story of Sodom must be balanced by that in Judges -- the "people of God" commit worse crimes that the most flagrant pagan, even to crucifying our own Lord! The Scriptures leave none exempted, but also bring all in (such is the beauty of recapitulation): the Messiah, crucified by the world and the people of God, is made alive and offers new life to those whom had murdered him, and all their descendants, whether Jew or Greek, slave or free, male or female.
However, this does not mean that I endorse any particular lectionary system. Being associated with the Anglicans here in Beaver County, I've had a little bit of experience with their system. It isn't perfect, as no lectionary can be. However, since the time of the early Church is past us, and we have seen a revival in interest in Jewish-Christian relations, it may be time to match up our readings with that of the old Jewish year, while still retaining, in full, the Christian year. This does not imply celebrating Jewish feasts (although reading the Megullah of Ester on Purim was extremely edifying), but rather remembering the olive tree in which we are grafted. If we were to match up our Gospel readings with the various Torah readings (John with Genesis, Matthew with Exodus, Acts with Deuteronomy, etc.) we might find vistas opened up in our relationship with our estranged older brothers in Abraham, we would see how the Messiah Jesus really is the "goal/apex of the Torah" as Paul puts it in Romans. Would this require a sizable amount of Bible reading daily and on Sundays? Yes. Would this require our ministers to bring their unwieldy sermons under control to fit all the readings and their expositions into a reasonable time frame? Yes. Would it require a greater understanding of Scripture by the common worshiper? Yes and amen, but it would build it also, especially if our translations were not wooden "religiousy" sounding blah-factories, but rather the earthy, allusive translations that these texts call for: ever had a pastor bring out the Greek or Hebrew about a passage and compare it with the language in another passage from a different book? Why don't our translations reflect those beautiful word-plays and obvious recapitulations of wording, rhythm, style? The Bible is essentially an aural book, meant to be read-aloud, to be chanted and sung, to be repeated until the words, rhythms, syntaxes, and allusions permeate our minds and shape our very way of thinking everyday.
Much work to be done, but it is good work for the people of God.