There are definitely some (mostly) young, carefree people who actually opt-in to that lifestyle. They're probably overrepresented near a University. They have friends and family they could go stay with to get back into society at a moments notice. I feel like they get conflated with people who "choose" homelessness because they have an addiction, or because the church that runs the shelter abused them as a kid, or because their schizophrenia makes them paranoid about social service workers. They need help to function in society, the same way an asthmatic would need help running a 5K.