I think this author has the cause/effect relationship backwards.
I think one reason teenagers have disappeared from the workforce is that: (1) they don't want to work, and (2) our country has come to rely on teenagers whose primary role is to be consumers, not workers.
This is starkly evident at towns up and down the New Jersey shore. Many businesses there employ seasonal labor from places like Ireland and Eastern Europe -- while American teenagers loaf around and spend long stretches of their summers down there patronizing the same businesses where their parents probably worked a generation earlier.
Ding, ding, ding, ding, we have a winner!
You make young adults wait years past when they WANT to do certain things, until they have lost all interest in doing them.
Most young adults WANT to get married when the are 14-16, but by their early 20’s have little to no interest in it anymore. Young children as young as 3 or 4 LOVE to work and help, but parents wont allow them. By the time they are in their early 20’s and told to go make their way in the world, they have no interest whatsoever in work, just eternal childhood.