I also was curious as to whether or not there was an official explanation. And I found a reference in the April 1977 edition of the New Era magazine, a faith-promoting Church magazine oriented towards teens and younger adults. Here is the applicable part of the guidance:
Perhaps the principal reason why the Church has not published or officially adopted the new translation is that the Prophet Joseph Smith was unable to attend to an authorized publication of it before his death. The Church records show that the Prophet wanted to publish the translation and was in the process of preparing the manuscript for that purpose at the time of his death but was hindered by persecution and lack of finances. As recorded in the Doctrine and Covenants, the Lord indicated that He wished to have it published. (See D&C 124:89.) It is also very probable that the Prophet would have made some additional corrections had he lived longer.
However, at the death of the Prophet Joseph Smith, the manuscripts and documents pertaining to the translation were retained by Emma Smith, the Prophet’s widow, who would not give them to the Quorum of the Twelve although Elder Willard Richards, apparently acting on behalf of President Young, requested the new translation of her. Consequently, when the Church moved to the Salt Lake Valley, it did so without the new translation of the Bible.
Subsequently, the Reorganized church (RLDS) was organized in Illinois, and in 1866 Sister Emma Smith gave the manuscripts into the custody of that church. In 1867 the RLDS published the first edition of the translation and obtained a copyright for it. The RLDS church still has the original manuscripts and the copyright and is therefore the sole publisher.
Since The Church of Jesus Christ of Latter-day Saints has had neither the original manuscripts nor the copyright, it would have been quite difficult, if not impossible, for the Church to publish the translation, even if it had wanted to. In Nauvoo in 1845, Dr. John M. Bernhisel made a partial copy from the original, and the Church has this in its offices in Salt Lake City, but it contains less than half of the corrections and is not suitable for publication.
Because the translation was published by the RLDS church, some questions have existed as to whether it had been published accurately. However, research in the past few years with the original manuscripts has indicated that the Inspired Version of the Bible, published by the RLDS church, is an accurate representation of the sense of the original manuscripts prepared by Joseph Smith and his scribes.
This explanation is still representative of "official" opinion in 2009, although since that time, we now much more explicitly proclaim the equality of the Bible in value to the other standard works, which include the Book of Mormon, the Doctrine & Covenants, and the Pearl of Great Price. This was necessitated to resolve the confusion resultant from our Eighth Article of Faith, which proclaims, "We believe the Bible to be the word of God as far as it is translated correctly; we also believe the Book of Mormon to be the word of God". Many believe the qualifier confers second-class citizenship upon the Bible, that we consider the Bible to be of inferior value.
This, of course, is not true. The statement "so far as it is translated correctly" is merely an explanatory clause acknowledging our belief that the Bible has errors, and is not a conditional clause suggesting inferiority in value. This is similar to the attitude strict Constitutional constructionists hold towards the "militia clause" in the Second Amendment, in which the militia clause is merely an explanatory clause rather than a conditional clause requiring militia membership in order to bear arms.
The LDS edition of the King James Version of the Bible is identical to the normal King James Version, except that it has cross-references to other LDS standard works. Some excerpts from the JST are included in the newest LDS edition of the King James Version. Expert LDS blogger Jeff Lindsay also presents Q & A about LDS usage of scriptures HERE.
Additional information about the Joseph Smith Translation can be found in Wikipedia. The online version of the JST can be found HERE.