Hobbies: an endangered species?

Their hobby might be practicing poses for a Le Penseur group photo.
#GreatRodinMoments

I read a couple interesting articles¹ today and learned that hobbies are apparently on their last legs! One begins:

Too many kids let screen time and homework crowd out real pursuits. If you ask most young people today if they have any hobbies, you will receive one of four answers:

1. "No."

2. "What do you mean?"

3. "Yeah. I play video games/watch TV/watch movies."

4. "Yeah..." and then they may actually cite a hobby.

The fourth is the least common.

But where exactly is the line between an activity and a hobby?