Because of the issues and accusations that the Devil, through the serpent, leveled against God in the Garden of Eden, and against humans in the Book of Job -- Genesis 3:1-6; Job 2:1-6
The issues that were raised, especially the issue of sovereignty, which was given credence when Adam chose to disobey... for them to be answered, would require time....enough time to allow man the opportunity to show whether he can rule himself successfully or not,
without God's protection and guiding hand.
Hence, life as we have it today...with all its ills and injustice.
But for those who
wanted God's influence in their lives, He gave us the Bible, giving us guidelines in how we should act and treat each other. For those who genuinely try to apply these in their lives, He also gives His spirit, the fruitage of which is "love, joy, peace, patience, kindness, goodness," etc. (Galatians 5:22-23.) Looking at the world in general, it's easy to see that most aren't applying it, and don't have Jehovah God's spirit.
Jesus
certainly had it, and gave us a great "model" to follow! -- 1 Peter 2:21
In addition to that, Jesus' life poured out in our behalf as a ransom (for those who want it), will eventually reconcile all willing creation back to God, and life
on this Earth (Isaiah 45:18; Matthew 6:9-10) will be as He intended -- peace between all creatures (Isaiah 11:6-9), and everlasting life for "mankind." -- Revelation 21:3-4
One of the greatest benefits, will be the Resurrection: the bringing back to life of most all humans who have ever lived,
even the wicked being given another chance. (John 5:28-29) This will rectify all the wrongs, wherein life was taken! All human family lines and relationships will be restored, if from that point on, they strive to be peaceable. If not, they will be destroyed forever, thrown into the "second death.(Revelation 20:14-15)" No more will wickedness be tolerated!
When all of this is accomplished, those issues will be settled once and for all! Then there will be peace forever! --Psalms 37:10-11,29.