First off, I would like to explain and invite you to consider that these missionaries, though unique, are just like you. It is just as awkward for them to knock on your door and invite you to listen to their message or ask you to read the Book of Mormon, as it is for you to receive them. Why then do they put themselves in such an uncomfortable position?
Believe it or not, I frequently ask myself the same question, and this is the best answer I can give you. My Reason is simple:
I KNOW that the restored Gospel of Jesus Christ found in its fullness, when applied, brings happiness and peace to the human soul and strength and joy to the family.
People might respond with, "you can't really 'know' Sister Bishop."
I would like to explain HOW I have come to know, but more importantly how anyone CAN "know" and WHY they would want to.
When anyone finds something that brings them an incredible amount of joy and happiness, their reaction is to share it with everyone they can. Grandparents share pictures of their grand kids to everyone that will look. Parents, when their child says something funny, usually make it their status of Facebook. The list continues with a favorite song or movie, great haircut, new shoes, favorite book, and so on. Many of these things bring me joy and excitement like everyone else, but of the things that matter most, (knowing that families can be together forever, knowing how to draw closer to my Heavenly Father, and partaking of the Atonement of Jesus Christ) has brought me the greatest joy and happiness I believe man can ever know.
I have come to learn for myself that the things that matter most are a personal relationship with God the Eternal Father, strength and unity in family, knowing how to repent, and consistently feeling God working in our lives as we strive to be something greater than we are.
I profess to you, that this is the essence of the message shared by missionaries of The Church of Jesus Christ of Latter Day Saints. Everything else they share of prophets in these days or The Book of Mormon, Another Testament of Jesus Christ, are only appendages to those truths of which I testify, and are wonderful means by which those blessing are available. They are evidence of Jesus Christ's work and organization today. Of these things I testify, in the name of Jesus Christ.