Psalms and Proverbs: why?

For many years now publishers have marketed New Testaments as independent volumes, often with the Psalms appended. There is evidently demand for such books, as they are considerably smaller in size than a complete Bible and thus more portable. The drawback is that, because the Scriptures tell the story of our redemption in Jesus Christ, we are getting only the final chapters of a much longer narrative. Owners of a New Testament are assumed already to know the earlier story and can thus make sense of a volume beginning with the coming of Christ into the world.

The addition of the Psalms to such a volume makes liturgical sense, especially when seen against the backdrop of the traditional one-year lectionaries used for centuries in both western and eastern churches. A look at the Book of Common Prayer's lectionary reveals the generous use of epistle and gospel readings for every sunday of the ecclesiastical year and, of course, the complete Psalter of Miles Coverdale, but very little from the Old Testament. One-year lectionaries have been used by Roman Catholics, Anglicans, Lutherans, and Orthodox churches, with preaching typically based on the gospel lesson for the day. Hence the publication of New Testaments with the Psalms fits into a traditional liturgical pattern familiar to most Christians.

However, around a generation or so ago, publishers began to add the Proverbs to these little volumes for reasons that I've not yet fathomed. These come in several versions, including the New International Version and the English Standard Version. I personally have two such books in my personal library: the ESV Vest Pocket New Testament with Psalms and Proverbs and a New King James Version published by Gideons International, now known as ShareWord Global.

Why add the Proverbs? The reason is not clear to me. As the Proverbs are little used in the liturgies of the major ecclesiastical communions, the need for their inclusion is not immediately evident. Might it represent a renewed emphasis on personal ethics within especially the evangelical world? Or might the connection often drawn between the presence of wisdom at creation (Proverbs 8:22-36) and Christ's presence at creation (John 1:1-18; Colossians 1:16) have prompted the book's inclusion? If another Old Testament book had to be appended to one of these little volumes, why not Isaiah, the second most quoted book after the Psalms by the New Testament authors? But if we pursue that line of reasoning, we put ourselves in the awkward position of deciding among different portions of inspired Scripture for an abridged Bible.

If anyone knows why the Proverbs were included in more recent editions of pocket New Testaments and Psalms, I would love to hear the story.