I believe that the Body of Christ must must go through the sufferings of the Cross to present to the world a Gospel that will be effective in saving their souls. I'm not sure that I understand everything in its complete eternal fullness, nevertheless I believe that Scripture makes it clear that this is a very vibrant and essential part of being a Christian.
There is a special Grace that is given to enable us to walk the valleys that God sets before us. Christians in persecuted countries who have endured torture and suffering pray for us in the West who have never known the grace that carries these saints. They pray that God will allow us to suffer persecution also so that we may experience the same grace that they have.
I will leave the theologians to argue all the why's and reasons. I will just present the Scriptures.
2Corinthians 4:8-12 We are troubled on every side, yet not distressed; we are perplexed, but not in despair; Persecuted, but not forsaken; cast down, but not destroyed; Always bearing about in the body the dying of the Lord Jesus, that the life also of Jesus might be made manifest in our body. For we which live are alway delivered unto death for Jesus' sake, that the life also of Jesus might be made manifest in our mortal flesh. So then death worketh in us, but life in you.
2Thessalonians 1:4,5 So that we ourselves glory in you in the churches of God for your patience and faith in all your persecutions and tribulations that ye endure: Which is a manifest token of the righteous judgment of God, that ye may be counted worthy of the kingdom of God, for which ye also suffer:
Galatians 5:11 And I, brethren, if I yet preach circumcision, why do I yet suffer persecution? then is the offence of the cross ceased.
Acts 14:22 Confirming the souls of the disciples, and exhorting them to continue in the faith, and that we must through much tribulation enter into the kingdom of God.
Romans 5:3 And not only so, but we glory in tribulations also: knowing that tribulation worketh patience;
Philippians 1:29 For unto you it is given in the behalf of Christ, not only to believe on him, but also to suffer for his sake;
Philippians 3:10 That I may know him, and the power of his resurrection, and the fellowship of his sufferings, being made conformable unto his death;
Colossians 1:24 Who now rejoice in my sufferings for you, and fill up that which is behind of the afflictions of Christ in my flesh for his body's sake, which is the church:
1Peter 2:21 For even hereunto were ye called: because Christ also suffered for us, leaving us an example, that ye should follow his steps:
1Peter 1:7 That the trial of your faith, being much more precious than of gold that perisheth, though it be tried with fire, might be found unto praise and honor and glory at the appearing of Jesus Christ:
2Timothy 1:8 Be not thou therefore ashamed of the testimony of our Lord, nor of me his prisoner: but be thou partaker of the afflictions of the gospel according to the power of God;
2Timothy 3:12 Yea, and all that will live godly in Christ Jesus shall suffer persecution.
Hebrews 13:12,13 Wherefore Jesus also, that he might sanctify the people with his own blood, suffered without the gate. Let us go forth therefore unto him without the camp, bearing his reproach.
Hebrews 11:24,25 By faith Moses, when he was come to years, refused to be called the son of Pharaoh's daughter; Choosing rather to suffer affliction with the people of God, than to enjoy the pleasures of sin for a season;
1John 3:13 Marvel not, my brethren, if the world hate you.