In October 2012, the president of our church, Thomas S. Monson, announced that the age requirement for missionary service would be lowered to 18 years old for young men and 19 years old for young women. Although missionary service is not mandatory, the opportunity to serve is one that most of our young people look forward to with great excitement. There are also older couples who choose to serve missions after their children are grown, but most LDS missionaries are about 20 years old. President Monson's announcement in October inspired a record number of young people to submit their applications for missionary service. Many of the missionaries you meet on this blog will be among the first to serve since the age requirement was lowered.
But the question still remains, why would these young people leave their homes, families, colleges, jobs and friends to serve as missionaries? Why would they devote two years (or 18 months for young women) of their young lives to studying, possibly learning a new language, meeting new people, and teaching about Jesus Christ and His restored Gospel? The answer is LOVE. Love for their Savior, and love for all of God's children, no matter where they live or what their circumstances might be. Gospel means "good news", and these young people are eager to share the good news with their brothers and sisters throughout the world. Their work is literally a labor of love.
More information about why Mormons serve missions.