The author is describing a general trend of domicile in American life, which is statistically[0] accurate. Most people who are in a stage of life where they can afford a detached home or mindset to buy one also have or are starting a family. I'm sure there's data to back up my claim somewhere.
[0]: http://www.nmhc.org/Content.aspx?id=4708, see the table "State Distribution of Apartment Residents, 2015", which shows that most US residents live in non-apartment homes.
[0]: http://www.nmhc.org/Content.aspx?id=4708, see the table "State Distribution of Apartment Residents, 2015", which shows that most US residents live in non-apartment homes.