Why did John the Baptist "cry out in the wilderness"?

Why did John the Baptist "cry out in the wilderness"?

You probably will not get a canonical answer to this question from Catholic scholars.

The truth be St. John the Baptist cried out in the wilderness because he grew up in the Judea desert or wilderness.

St. John the Baptist was only a few months older than Jesus was. We have no record of his childhood, but it’s a reasonable speculation that the two boys, who were relatives, would have known each other and spent time together.

As for his escape from Herod’s slaughter of the Holy Innocents, St. Peter of Alexandria (311) speculated that, to be spared the wicked King Herod’s wrath, the young John was taken into the desert, where he lived until many years later, when he came preaching repentance (see Mark 1:2–4).

Blessed Catherine Emmerich seems to support this idea in her Revelations concerning John the Baptist:

Elizabeth takes John into the Wilderness

Zechariah and Elizabeth had also received a message warning them of imminent danger. I think the Holy Family had sent them a trusty messenger. I saw Elizabeth taking the little John to a very hidden place in the wilderness, a few hours' distance from Hebron. Zechariah accompanied them for only a part of the way, to a place where they crossed a small stream on a wooden beam. He then left them and went towards Nazareth by the way which Mary followed when she visited Elizabeth. I saw him on his journey to Nazareth, where he is probably going to obtain further details from Anna. Many of the friends of the Holy Family there are much distressed at their departure. Little John had nothing on but a lamb's skin; although scarcely eighteen months old, he was sure on his feet and could run and jump about. Even at that age he had a little white stick in his hand, which he treated as a plaything. One must not think of his wilderness as a great desert of waste sand, but rather as a desolate place with rocks, caves, and ravines, where bushes and wild fruits and berries grew. Elizabeth took the little John into a cave in which Mary Magdalen lived for some time after Jesus' death. I cannot remember how long Elizabeth remained here hidden with her young child, but it was probably only until the alarm about Herod's persecution had subsided. She then returned to Juttah, about two hours' distance away, for I saw her escaping again into the wilderness with John when Herod summoned the mothers with their little sons up to two years of age, which happened quite a year later.

What we do know for fact comes from the Gospels:

3 And in those days cometh John the Baptist preaching in the desert of Judea.

2 And saying: Do penance: for the kingdom of heaven is at hand.

3 For this is he that was spoken of by Isaias the prophet, saying: A voice of one crying in the desert, Prepare ye the way of the Lord, make straight his paths.

4 And the same John had his garment of camels' hair, and a leathern girdle about his loins: and his meat was locusts and wild honey.

5 Then went out to him Jerusalem and all Judea, and all the country about Jordan:

6 And were baptized by him in the Jordan, confessing their sins. - Matthew 3:1-6

The Catholic Encyclopedia admits that we do not know how long he preached in the wilderness, but that he indeed prepared away for the Lord though his preaching and holiness.

The Precursor had been preaching and baptizing for some time (just how long is not known), when Jesus came from Galilee to the Jordan, to be baptized by him. Why, it might be asked, should He "who did no sin" (1 Peter 2:22) seek John's "baptism of penance for the remission of sins" (Luke 3:3)? The Fathers of the Church answer very appropriately that this was the occasion preordained by the Father when Jesus should be manifested to the world as the Son of God; then again, by submitting to it, Jesus sanctioned the baptism of John. "But John stayed him, saying: I ought to be baptized by thee, and comest thou to me?" (Matthew 3:14). These words, implying, as they do, that John knew Jesus, are in seeming conflict with a later declaration of John recorded in the Fourth Gospel: "I knew him not" (John 1:33). Most interpreters take it that the Precursor had some intimation of Jesus being the Messias: they assign this as the reason why John at first refused to baptize him; but the heavenly manifestation had, a few moments later, changed this intimation into perfect knowledge. "And Jesus answering, said to him: Suffer it to be so now. For so it becometh us to fulfil all justice. Then he suffered him. And Jesus being baptized, forthwith came out of the water: and lo, the heavens were opened to him. . .And, behold, a voice from heaven, saying: This is my beloved Son, in whom I am well pleased" (Matthew 3:15-17).

One of my most thoughtful passages of St. John’s Gospel comes from St. John the Baptist concerning Jesus:

25 And they asked him, and said to him: Why then dost thou baptize, if thou be not Christ, nor Elias, nor the prophet?

26 John answered them, saying: I baptize with water; but there hath stood one in the midst of you, whom you know not. - John 1:25-26

Jesus must have been able to blend in without any fanfare at all and must have looked like everyone else, in the presence of the Precursor.

In the end St. John the Baptist must be a voice crying out in the wilderness, because it is his home. How many times has God spoken to the Prophets in the wilderness such as Moses on the Mount Sinai.

The short answer is: because God told him to!

Some commentators associate the Messianic promise of Hosea 2:14-15 with John the Baptist:

Therefore I am now going to allure her; I will lead her into the wilderness and speak tenderly to her. There I will give her back her vineyards, and will make the Valley of Achor a door of hope. There she will respond as in the days of her youth, as in the day she came up out of Egypt.

Thus the choice of wilderness is prophesied and in that passage makes reference to the Exodus, when Moses led the people out of slavery and into the desert. Thus the Messiah is a new Moses. Moses' spokesperson was Aaron, so Aaron corresponds to John and Moses to Jesus.

A prophecy from Isaiah is also associated with John the Baptist:

A voice of one calling:
“In the wilderness prepare
    the way for the Lord;
make straight in the desert
    a highway for our God." (Isaiah 40:3)

John's ministry was one of preparing people to receive the Messiah.

Of course, Handel put it so poetically in his masterpiece, The Messiah:

Comfort ye, comfort ye my people, saith your God. Speak ye comfortably to Jerusalem, and cry unto her, that her warfare is accomplished, that her iniquity is pardoned. The voice of him that crieth in the wilderness; Prepare ye the way of the Lord; make straight in the desert a highway for our God.