why do people run away?

i often wonder what makes kids want to run away from home or adults to just venture away? what seems so good about leaving your surroundings when there isn't any known Problem per se? makes me wonder why we all go through that phase where our friends or somebody in our family etc.... just seems to have it going on and what we have isn't up to par. what is the motivation and is it something that you feel out of the blue or is it something you plan in advance? as a kid I wanted to run away for various reasons but it was nothing about what another friend or somebody i was related to that made me want to leave. i feel for all the Kids and adults on the missing file. what drives anybody to want to really leave? there are many things that go through our mind. what are we hopjng to find and what is the ultimate goal?