I suspect this is related to the new developmental life phase called "emerging adulthood" posited by developmental psychologists:

http://www.nytimes.com/2010/08/2...

We’re in the thick of what one sociologist calls “the changing timetable

for adulthood.” Sociologists traditionally define the “transition to

adulthood” as marked by five milestones: completing school, leaving

home, becoming financially independent, marrying and having a child. In

1960, 77 percent of women and 65 percent of men had, by the time they

reached 30, passed all five milestones. Among 30-year-olds in 2000,

according to data from the United States Census Bureau,

fewer than half of the women and one-third of the men had done so. A

Canadian study reported that a typical 30-year-old in 2001 had completed

the same number of milestones as a 25-year-old in the early ’70s.

This is not unprecedented. "Adolescence" emerged at the turn of the 20th century due to industrialization and universal high school education, in America. Dev psych life stages are a function of culture.