Because we fell. If we would have just fallen from a tree we could simply climb up again. But we fell from our relationship with our father. We have become arrogant and are going our own ways.
Why is there evil and suffering in the world?
The evil and suffering is caused by sins. In the beginning, the world God created was good, there’s no evil and suffering. But an angel fell, he didn’t want to obey God but to become God. He tempted human being and they sinned and fell. The sin means the relationship was broken. The evil is from the devil and the human, they did the wrong things with their free will. And the suffering is from the sins, because the sin is to break the law of life, and it will bring all kinds of suffering. For example, if one person didn’t wear enough cloth, he might get cold and suffer disease.
God never created sin but Satan put sin inside the world God created.
Looking at the Bible and Genesis, we can know that at first the creation of God, God created a very beautiful Garden of Eden. But people are falling. Because the world of sin has been wicked and painful, but God has not given up on man, God has continually saved, and the world will be restored to what God originally created. This is God’s intention.
All these come from sins.
Sin cause suffering. That’s not God’s will. God first created a perfect world of love, joy and peace, however, angel Lucifer fell and became Satan. He tempted Adam, Adam fell so sin began to enter into the world, therefore we suffer.