The internet lets a person leave a room without leaving the conversation.

You can be in a room with people and simultaneously somewhere else entirely, mid-argument, mid-joke, mid-scroll. The body remains and the attention has gone, which is a new thing in human history and one that everyone present can feel even when nobody comments on it.

Watch for the moments when you leave without leaving, particularly with people you care about. Putting the phone in another room for an hour is unsubtle and works. The point is not discipline for its own sake, it is being actually available to the people you are physically with.