A horse is always trying to do what it is thinking. So when a horse thinks to do something you want, it looks like you did nothing. There is no more important principle in good horsemanship.
I try to watch as many horse people working with horses as my busy life permits. In particular, I am always interested in observing other professionals to see what they do that maybe I could adopt or do better.
Once upon a time round yards were only to be found on the properties of professional horse people. They were very commonly used by racehorse breakers and a few old bushies.