Why cover the crosses and statues?

In the Cathedral, from the Fifth Sunday of Lent until the Easter Triduum, we continue the custom of covering the crosses and statues with a purple cloth. It has been a universal custom in the Latin Church since at least the 17th Century and, even though it is no longer mandatory, it is still a permitted and praiseworthy practice. 
For the Fifth Sunday of Lent the Roman Missal says, "In the Diocese of the United States, the practice of covering crosses and images throughout the church from this Sunday may be observed. Crosses remain covered until the end of the celebration of the Lord's Passion on Good Friday, but images remain covered until the beginning of the Easter Vigil."

But why do we do it?

History of the custom
The custom finds is origin in the 9th Century. In Germany Christians put a large cloth in front of the altar from the beginning of Lent. The cloth hid the entire altar from the view of the faithful and was not removed until the reading of the Passion on Wednesday of Holy Week when the phrase "the veil of the temple was rent in two." Eventually this custom was extended to crosses and statues. Later, in the 17th Century, this custom became universal and was limited to the "Passiontide" which began on the Sunday before Palm Sunday which was then called "Passion Sunday" and is now the 5th Sunday of Lent.
It is interesting to note that before the Second Vatican Council the Gospel that was read on "Passion Sunday" (now the 5th Sunday of Lent) was from St. John, chapter 8. The last verse of that Gospel passage says, "So they took up stone to throw at him; but Jesus hid himself, and went out of the temple." In other words, Jesus hid himself from the Jewish authorities and is now hidden from the world as He prepares for His impending passion and death. 

The suffering of Christ "veils" His divinity
The nearness of the hour of Christ's suffering causes the Church to veil His image and those of His saints as a way to mystically enter into the humiliation of Christ and how His divinity is about to be hidden from view or "veiled" in order to bring about our salvation. On the Cross we struggle to "see" that this is God who suffers and dies for us. The veiling represents how Christ has veiled or "hid" His divinity by humbling becoming man and taking on human suffering. 

The suffering of Christ "veils" His humanity
He has also "veiled" His humanity in the sense that the depth of the cruelty against Him was so severe that His humanity was dramatically disfigured. In a prophecy about the suffering of the Messiah Psalm 21: 7 says, "I am a worm, and no man; scorned by men, and despised by the people." On the Cross even the humanity of Christ was disfigured and veiled. His face and His entire body was distorted by the many blows, scourges and nails that Jesus was scarcely recognizable, even in His humanity. 

The Cross "veils" its victorious meaning
As Christians, we know that the Cross of Christ is a sign of God's victory over death. We even have a feast called the Exaltation of the Holy Cross. But as we approach Holy Week and veil the Cross, we express how difficult it is without faith in the Resurrection to "see" this victory. The Cross' true meaning is "veiled" from the eyes of those who do not believe in Christ who is truly human and truly divine and has died and rose for our salvation. At first sight, the Cross does not seem to be a sign of victory but only of humiliation and death.