If you want to read the best treatise on the changing use of the Book of Mormon, read "By the hand of Mormon", By Terryl L. Givens (I believe). Summarizing it does it a disservice, but it tracks how we have used the Book of Mormon over the years.

One of his major points is that in the early days, the Book of Mormon wasn't preached from often. But most read it before conversion. It's very existence, and correlation with the Bible was the "marvelous work and a wonder" that was taught. The doctrine, at the time, was considered in harmony with the Bible.

The Book of Mormon was studied concurrently with the other standard works. I am not that old, but we routinely read one as a family, until it was finished, and then moved on to the next book of scripture.

Shortly after President Bensons talk, there was a lot of emphasis on reading the book of Mormon continuously. The doctrines that is "the most correct book on earth" and that it would lead the reader of it closer to god than any other book pre-date this talk. As does the article of faith proclaiming, "We believe the Book of Mormon to be the word of God, we also believe the Bible to be the word of God as far as it is translated correctly." Both teachings come from the time of Joseph Smith.

I can't say the Book of Mormon was ignored, but I believe that as a culture, scripture reading had/has become passé. We read essays and historical accounts, we read a lot about the scriptures, but not as much IN the scriptures (I would include myself in this).

I believe this affected the emphasis on Book of Mormon reading in the Missionary program first, and has had a much wider effect on the church as it lead to a lot of success.

President Hinkley also had several periods where he "called us to repentance on this matter".