Humans were creatures of immense adaptability.
Even though threats loomed over them daily, people numbed their emotions, considered disasters as "normal," and rationalized their fears and despair with a self-hypnotizing optimisim. Eventually, they became accustomed to and understood their situation; pain and despair were no longer recognized as such. New, distorted values interpreted these experiences as redemption and trials, necessary paths to happiness.
This was utterly meaningless.
The stimulation of fear needed to maintain a certain freshness to prevent it from morphing into anger and resilience. By torturing the target with fear akin to standing on the edge of the Abyss, distractions from crucial details were ensured, achieving the ultimate goal before complete destruction ensued.