I've been wondering this since reading Franny and Zooey.
From what I can tell in the first part of the 1900's, young men were expected to live at home unless they found work far away or married. Around the 1960's it became more normal to move out once they hit adulthood. Is this accurate?
/u/pipkin42 has written an awesome answer about the history of men living in hotels in the late 19th-earlier 20th century--both practical aspects and the social significance of it.