What was the reason for the harsh punishment of slaves for minor offenses?

In "Narrative of the Life of Frederick Douglass, we learned about the harsh punishments slaves recieved for small offenses. The question is, why is this the casse? Well, the easy answer would be that slave owners wanted to keep the slaves under control through fear. However, while I believe that was definitely a factor, I don't think it's a story. First, as Douglass pointed out, many slave owners were very cruel and just enjoyed giving out punishment. Also, there is another important factor he hints at. When he talks about his new master, he explains that even though at first she was very nice, soon, she became cruel. While he doesn't go into more detail, this makes it clear that many slave owners just gave out harsh punishment because they had the power to do so. Perhaps this points to a greater issue with humanity, but the point I really widh to make is that keeping slaves under control was not the sole reason for slave owners dealing out harsh punishment for minor offenses.