"Is God willing to prevent evil, but not able? Then he is not omnipotent. Is he able, but not willing? Then he is malevolent. Is he both able and willing? Then whence cometh evil? Is he neither able nor willing? Then why call him God?"

Such questions presuppose that one can understand the motives of an infinite being. Standard theology suggests that God allows suffering because it builds character, thus doing more overall good than harm. Of course, that's just idle speculation because there are no supernatural beings.