Harry had learned a lot from being the target of the Leglimens spell. So, he used it on Severus without touching him. Unearthing memories from his first advisor was like walking through a hall of mirrors observing something too similar to his childhood. Things hit far too close for comfort. They repeated that lesson two more times. Then Harry had had enough. Although the Horcrux told him that gaining leverage over a follower could be helpful. However, the teenager had no interest in gathering more memories of torment through the eyes of another.