It was not common to follow a teacher fulltime. The reason for following Jesus fulltime is not stated, but it is obvious to think of their unimaginably important task: to be the foundations of the church, coregents and judges with Christ and judges (Ephesians 2:20; Revelation 4:4; Revelation 21:14; Matthew 19:28). They also largely determined the content of the New Testament (John 14:25–26).
18 While walking by the Sea of Galilee, he saw two brothers, Simon (who is called Peter) and Andrew his brother, casting a net into the sea, for they were fishermen.