People are scared to report corruption because they fear for their lives as well as their family's lives.
People, who are corrupt, are criminals. This is because corruption is a crime. Corruption is against legal laws and moral laws. If people are capable of being corrupt, then they will also be capable of inflicting pain to people who reported their corrupt activities. They will do anything and everything to avoid getting caught and implicated as well as to ensure the continuance of their corrupt activities.