Young adults are soft, poor, spoiled and want to carry stuff (surfboards, skis, drum sets,...). Motorbikes don't fit their lifestyles.
My teenager expressed interest in riding. So, I offered that he could take the safety course and ride an underpowered trail bike (say, a TW200) to high school for a year, then I'd think about letting him ride a proper motorcycle. He wanted nothing to do with it. Too wet, too cold, not cool enough...
1974 R90/6 motor w/1050 kit; twin plugged; installed in...1970 R60/5 frame; RM125 front end; KZ1000 Police Tank.