God has our best at heart and is ultimately in control. Detour signs reroute traffic on a highway. In the same manner, along life's road, God posts detour signs. When God does, it is not wrong to ask, "Why, God?" God will either reveal an answer in his timing, or if not in this life, then definitely in the hereafter.
There are several reasons I feel God posts detour signs on life's road. Perhaps, first of all, God foresees danger ahead of us. Since God is omniscient, for he knows all things, God has our best at heart. God may foresee an unpleasant experience for us and want to avert it. To some, God permits tragedy, which is a mystery to them. 1 Corinthians 2:16 says, "For who has known the mind of the Lord that he may instruct him? But we have the mind of Christ." If our hearts are "deadened" to God's voice, we will not hear him when he speaks to us. Second, God posts detour signs in our life since he has a plan and purpose for us. That plan may entail pain or persecution.
Pain is meant to mold and shape us, to mature us and make us more like Christ and think his thoughts. His thoughts are only love and humility - all the fruits of the spirit. Corrie ten Boom's life was turned in a different direction when she and her family were captured by the Nazis.
God also posts detour signs in our life for our betterment. God leads and directs our lives. I don't believe in luck or coincidences. Things in life happen for a definite reason. God may arrange our lives in such a way that we receive Christ as our Lord and savior personally. God knows our hearts. God knows his sheep (people) and calls them by name. I will close with Romans 8:28. "And we know that in all things God works for the good of those who love him who have been called according to his purpose."