When you're out and about in the city during the day, who are all these other people who seemingly have nothing to do all day but putter about town? "Many people I encountered reported variations on the 'in-between jobs' line, and it's not just a euphemism. Among the employed are those who will soon be without work, thanks to frictional unemployment, the inevitable periods of joblessness structured into even perfect economies."
Update: An episode of This American Life from 2000 tackled the same subject, with a focus on Manhattan. "All those people you see in the middle of the workday, in coffee shops and bookstores? Who are they? Why aren't they at work? Reporter George Gurley tackled these tough questions. On four separate days, he interviewed these loafers in New York." (thx, michael)