Why wasn't Noah's wife name revealed?

The Jewish Book of Jubilees has the following verse, which I feel answers your question:

And in the twenty−fifth jubilee Noah took to himself a wife, and her name was Emzara, the daughter of Rake'el, the daughter of his father's brother, in the first year in the fifth week and in the third year thereof she bare him Shem, in the fifth year thereof she bare him Ham, and in the first year in the sixth week she bare him Japheth. - Jubilees 4:33

So if you consider the teachings of around Christ's time and beforehand also inspired by the Lord (which most do) then this would be your answer.

An answer for the original question "How do Theologians explain that there is no name for Noah's wife."

Jewish theologians explain it this way: The identification of Na'amah, a descendant of Cain, as the wife of Noah, solves the structural flaw in Genesis as well as the above mentioned theological problem. The family of Cain is described at length in order to reveal the identity of the second mother of mankind. Her name indicates that she deserved to survive. Since mention of her family background would not have been complimentary to her, her name is not given in the present story. From her being saved it becomes clear that not all the descendants of Cain were without hope of redemption and therefore Cain received Divine Revelation.

Rabbi Naftali Tzvi Yehuda Berlin comments in his commentary Ha'amek Davar on Genesis 4: 32 "from that which was good in Cain the world was established, through this woman, and he had the privilege of joining in the survival of the world with the seed of Seth, who were the purpose of creation".

Neither Roman Catholics nor just about any other Christian denominations believes that the Bible contains every detail possible. As John writes, These things are written that you might know that Jesus is the Christ.

Just about every accepted theory of inspiration suggests that the Bible that the words we have are "sufficient" (and that is the Theological(TM) term) - meaning they are enough - not exhaustive. Evangelicals are more likely to harp on things like sola scriptura than Catholics who believe in the Magesterium - but even they would reject the need for such a minor detail.

As Mark Shea, a catholic apologist writes:

Material sufficiency means that all the bricks necessary to build doctrine is there in Scripture. However, it also teaches that since the meaning of Scripture is not always clear and that sometimes a doctrine is implied rather than explicit, other things besides Scripture have been handed to us from the apostles: things like Sacred Tradition (which is the mortar that holds the bricks together in the right order and position) and the magisterium or teaching authority of the Church (which is the trowel in the hand of the Master Builder). Taken together, these three things -- Sacred Scripture, Sacred Tradition, and the Magisterium -- are formally sufficient for knowing the revealed truth of God.

(in Not by Scripture Alone, edited by Robert A. Sungenis, Santa Barbara, CA: Queenship Pub. Co., 1997, chapter 4: "What is the Relationship Between Scripture and Tradition?," 169-210; quote from 181-182)

In Pope Clement XI's Prayer for all things necessary for salvation, for example, supplicants pray:

I beg of Thee to enlighten my understanding, to inflame my will, to purify my body, and to sanctify my soul.

Give me strength, O my God, to expiate my offences, to overcome temptations, to subdue my passions, and to acquire the virtues proper for my state.

Fill my heart with tender affection for Thy goodness, hatred for my faults, love for my neighbour, and contempt of the world.

The name of Noah's wife is exceedingly unlikely to inform any of these things.