'Idle' adults do the same, and it's worth pointing out that young teenagers aren't permitted to contribute to society in other meaningful ways e.g. by getting a job if they can and prefer to.
Of course they can contribute: they can help their families with day-to-day tasks, join scouts or other volunteer groups, help friends with homework. We had a Spring Cleaning day at my kids' school where about 25 teenagers scrubbed the bathrooms, painted over graffiti, washed windows, and decorated bulletin boards.
I don't wish to imply that getting a job is the only meaningful thing a teen could be doing. However there are plenty of teens who would love to get paid jobs as say, programmers. They are denied because of old laws intended to prevent poor families forcing kids into mines or factories for twelve hours a day. Yet most of what teens are coerced into doing at present is 'make work'. It is this fact which explains the lack of motivation, not idleness or some kind of pathology requiring 'intervention'.