Think of the ancient Aztecs. They could see that they had angered their dozens of god (the evident suffering, disease, and death), so they would try and appease them with a "payment." They would take the most precious thing they had–a handsome youth, or a beautiful virgin, and they would sacrifice them on a bloody altar to try and make atonement. However, the Bible says that any sacrifice we make is an abomination to God (especially human sacrifice–God Himself stopped Abraham from sacrificing his son). Besides being a murderous act, human sacrifice offers a tainted sinful blood. It would be like me offering a judge drug money to pay your fine.