Why did the Friend of the Bridegroom Not a Become a Disciple?

Only John the Baptist knew Jesus to be the incarnate Son of God, but the Forerunner did not follow him.

The Gospel passage assigned by the lectionary for the Second Sunday of Advent is Luke 3:

In the fifteenth year of the reign of Tiberius Caesar, when Pontius Pilate was governor of Judea, and Herod was ruler of Galilee, and his brother Philip ruler of the region of Ituraea and Trachonitis, and Lysanias ruler of Abilene, during the high priesthood of Annas and Caiaphas, the word of God came to John son of Zechariah in the wilderness. He went into all the region around the Jordan, proclaiming a baptism of repentance for the forgiveness of sins, as it is written in the book of the words of the prophet Isaiah, "The voice of one crying out in the wilderness: 'Prepare the way of the Lord; make his paths straight. Every valley shall be filled, and every mountain and hill shall be made low, and the crooked shall be made straight, and the rough ways made smooth, and all flesh shall see the salvation of God.'"

John the Baptist is a prominent and essential character not only in the Gospels but in the church’s liturgy, art, and iconography. Like a familiar painting that has hung on the wall so long its beauty and detail no longer elicit astonishment, during Advent the church often rushes past John the Baptist without attending to the remarkable implications of the evangelists’s presentation of him.

The fact is as simple as it is straightforward, yet the church seldom notices it:

John baptized Jesus.

But John did not become a disciple of Jesus.

John the Baptist had a different vocation than discipleship.