Scripture, by nature, assumes a commanding, authoritative voice. We turn to scripture for truth, for that truth distilled into dogma, for that dogma distilled into ritual. As such, we expect scripture to read as the voice of God--flawless, omniscient, and absolute. And much of the Bible does indeed use this voice.
Many Book of Mormon orators, however, try not to build themselves up as they speak, but rather downplay themselves. They point out their own flaws and limits. King Benjamin says, "I am like yourselves, subject to all manner of infirmities." (Mosiah 2:11) Enos and Alma speak of their struggles with sin before God. Nephi says, "O wretched man that I am." (2 Ne. 4:17) This appears to be the common denominator of many Book of Mormon leaders--they dissuade the reader from thinking of them as perfect, and encourage the reader to listen more to their teaching.
Why did they do this? It can be a little intimidating to talk to someone who is larger than life. But when the person you meet is closer to your level--not sinless but sin averse--then it is easier to accept their message. You feel more connected with them, more willing to listen and receive. These Book of Mormon speakers really nail that; it's easy to imagine them as humans, perhaps not knowing all truth, but like their readers, trying to find it.
Thinking of the Book of Mormon as their stories--the stories of imperfect people--can help humanize the book, and make it less intimidating. We can see its stories as our own story, and find ourselves in its pages.