Why does God allow suffering?

Sin

Sin’s consequences are separation from the goodness of God. This is usually exhibited by suffering. Hebrews 12:17 speaks of the ordeal of Esau after he exchanged his birthright for a morsel of bread. It says, “Afterward, as you know, when he wanted to inherit this blessing, he was rejected. He could bring about no change of mind, though he sought the blessing with tears. These tears from Esau came after the realization that what he had taken for granted was beyond recovery. The misery that he endured for the sin of compromise was great.
The agony of being apart from God is great. Sin will cause great suffering until repented. It was not for naught the Judas had to hang himself after betraying his Master. David cries in Psalms 32:12 When I kept silent, my bones wasted away through my groaning all day long.