What are the phsychological motives behind people, especially young ones, choosing to live on the streets voluntarily?
I agree that you probably need information from someone educated in this topic, but if I were asked this as a question on a test, I could speculate logically. Perhaps the person objects to the restictive nature (or seemingly) of his or her homelife. Perhaps the individual doesn't feel validated in more structured setting, and the loosely organized system of "family" on the streets is more appealing. It's possible that some suffer from other issues.
I agree that we can speculate with some accuracy, but a better approach would be to do some research. I, too, thought of escape as a primary reason for teens who end up homeless on the streets. Escape from abuse, authority, or whatever other real or perceived problems would, I think, be motivators for an impulsive or desperate young person to leave. The second thought I had was the simple idea of independence--breaking away from the "controls" and restrictions of their homes. I'm confident plenty of research has been conducted on this subject, and I wish you the best as you further explore it.
I would suggest that this is a topic that requires research. Anecdotal narratives can provide much in way of guidance on such an issue. From this, I think we can pull out that many children "choose" to live on the streets as a way to escape their home condition. Some flee for reasons of abuse or neglect, as well as the basic idea of feeling unloved. I am not certain that kids leave homes and live on the street because "they want to." Rather, there are conditions that prompt them to believe that living on the streets is a better alternative than what they are facing in their current living conditions. Part of this feeds into the adolescent desire to be free, but I think that this is where the desires of adolescence inadvertently impact judgment.