I zone out constantly, although I keep myself from doing it more now than when I was a child. It is both helpful and inconvenient at work... helpful in that I totally block out what is around me and I don't hear people talking, but not helpful in that people try to get my attention or talk to me and I don't notice them. When I am not supposed to be doing something, like if I am by myself at the beach or in the woods, or even at home looking at the wall, I find it very relaxing and calming.
When I was a kid my parents thought I was intentionally ignoring them or avoiding doing things I was told. I would zone out when being addressed (also I hadn't learned at that point that you are supposed to respond when someone is talking to you by nodding, looking at them, etc to indicate you are listening, so sometimes they thought i was zoned out when I really was listening). Also I would tend to stop whatever I was doing to stare at something and think. Sometimes I would be going for a walk and would stop to look at something and start thinking and get in trouble becuase I was late getting back.
Nowadays I try to catch myself so I do not start thinking about something when I am getting ready to go somewhere in the morning, etc becuase I will not get there on time. I am usually concentrating on an object when I "zone out," although my mind doesn't necessarily stay on what I am looking at. I also do it as sort of a protective measure when I am around a lot of people and they are making me nervous, so I can close them out and concentrate on just one thing. Often I find myself nodding my head when I am zoning out, which I try to stop if I notice.