Teens are basically doing less of everything because of the phones. Alcohol, sex, getting a drivers license, going to movies, basically any activity you could name has declined rapidly starting around 2012 when phones became ubiquitous.
If you consider sex, drugs, and alcohol to be forms of "stuff to do" then it sorta sounds plausible but why driver's licenses? Why not sports or extracurriculars? Why not video games? Why are tabletop rpg getting more popular?
You could just as easily blame ubiquitous access to porn for most of this as well and it would be just as plausible.
Teens are living their lives vicariously through other people. Capitalism has finally created the perfect consumption slave. They buy what they're told to buy via peer pressure feedback loops and stay at home contended with their entertainment bubble.
Anecdotally from my social circles: youth already hang out online, with any or all of their friends at the same time. Why go somewhere just to see fewer people? And once you're there, are you going to do something besides chat and play games, which works fine online?
Older generations saw a driver's license as freedom, but younger generations don't see as much appeal in what a licensed driver is free to do.
You can also still get the half-gallons of super cheap vodka, but getting that is more difficult because you need someone who is 21 to procure it for you.
Memes about permanently stoned people are spreading fast. Propaganda about "cool" hippies does not work any more.
The same with myths around sex, real anti-conception effectiveness...