Why did God require the shedding of blood?
God, being sovereign, demanded the shedding of blood for His own reason, a requirement people may find gory but which He can ordain as He sees fit. The animal sacrifices were examples pointing forward to the one that could take away sin; their blood could not, but the blood of Christ could.
Les explains that many people may frown at this as a gory concept, but God is sovereign and can do as He sees fit. For His own reason He demanded that there had to be the shed blood. The animal sacrifices were looking forward to that; they were examples of it, but those animals' blood could not take away sin. They looked forward to the one that could, and that was the blood of Christ.