Those aren't teachers. Those are just sadists who work in a teaching position. I've known at least one of them, and it's true. They quit when they had their classroom power taken away from them by policy changes. They never cared about kids and weren't interested in teaching. They just wanted power and could never acquire it with adults, so they chose to exert power over children instead.
The one I knew personally complained about the policy removing corporal punishment, and necessary promotion of failing students to free up seats for next year's kids. That was all it took to make them quit.