The book of Mark was written by a follower, though not an original disciple, of Jesus. John Mark received much of his information from Peter, who was an original disciple of Christ.
Mark writes with a different intended audience, the Romans and Gentiles. Therefore, details about Jesus' lineage and prophesy was not the focus but rather the service and sacrifice that Jesus offered. At the time that Mark writes, possibly in Rome, Christians were being persecuted.
The book of Mark tells a great deal about the acts of Jesus and the hope that Jesus brings to those who believe in Him. Mark contains actual Aramaic phrases, spoken by Jesus.
The emphasis in Mark is on Jesus' acts of healing, service and teaching.
Mark also offers strength for the persecuted, Mark 10:29 "I tell you the truth," Jesus replied, "no one who has left home or brothers or sisters or mother or father or children or fields for me and the gospel will fail to receive a hundred times as much in this present age (homes, brothers, sisters, mothers, children and fields-and with them, persecutions) and in the age to come, eternal life. But many who are first will be last, and the last first."
This provides just one scripture-verse to explain why many sacrificed their own lives for the truth, hope and beauty that Jesus offered.