I've been paying very close attention to things in my neighborhood this year. We are about 50 houses over a 3 block area. About 1/2 of these houses have 1 or more kid under the age of 15 residing within them. About 1/4th are empty nesters (like my wife and I), and the rest are either newlyweds, or retirees.
On evenings and weekends, it can be like a ghost town. Kids just don't play outside anymore.
I'm not imagining this - it's absolutely true. I built my neighbor an elaborate 2-story play house for his (then) kids about 10 years ago. It took me 2 full weekends and I copied a pattern at Lowes and built it for him for about 1/4th the cost. They never played in it. Never. For years, I'd watch outside the kitchen window, staring at the playhouse, thinking about how cool that would have been for me and my brother when I was their age....
The point is this - kids now get their "adventure" from a screen. They are over stimulated to the point where anything short of Disney world is boring to them.
Motorcycling is an adventurous activity. For kids and young adults, it's a discovery of a new dimension of freedom and adventure. It physically (not digitally) stimulates all of your senses and opens your world up in all directions. But younger people don't care about that - they quite literally can't see the forest for the trees.
If the motorcycle industry is dying, demographics and marketing has everything to do with it, IMO. I hope that I'm wrong.