The idea is social isolation, which could lead to loneliness in public and crowded places like parties, metros, etc. Fear of the others, negative self-steam and/or lack of consistent human contact could be our conscious choice. Many of us prefer to take a lonely space in public. It could have different reasons. In fact, we choose to be alone in a crowded place, and we kind of play/ enjoy our self-conflicts in these occasional contacts with our environment.