I think there are at least two kinds of "content" -- one that stems from happiness and another that stems from depression.
The former is the good kind, the one we all assume the article is talking about.
The latter is a resounding "meh" followed by a "who cares."
I've seen a lot of the latter in people in their 20s and early 30s here. The world's going to shit, the society's going to shit, nobody has money, rent is expensive, nobody cares. Spend the money now and enjoy hanging out with friends -- screw retirement and the future because you can deal with it later, preferably with the pension system.
Who's going to get ahead at work? The old folks are all impressing their own power structure on the younger folks and making life miserable. Why bust your ass at work when you can just do your own thing with a bunch of jobs cobbled together?
So, basically, a lot of the "content" people I see around me around happy with their lot, they just don't think their lot's going to improve or worth working on.
This is from a point of view of 11 years in Japan, six years in Tokyo.