Something I think has to be considered here is that "hanging out with your friends" is, like most things kids do, a contingent activity. It requires parents to allow it.
And increasingly parents are absolutely unwilling to let their kids out of their sight. Everything must be managed or supervised.
I'm an older millennial. My niece and nephew are ten and seven respectively. They live in the same housing development my brother and I grew up in. Lots of kids their own age there, and woodland with town-maintained paths to wander in.
When I was seven I thought nothing of telling my mom "Mom, I'm going out" and getting on my bike and going wherever. Maybe my friend Steve was home. Maybe Priscilla was climbing up that one cool half-fallen tree in the forest. Maybe I'd just pile rocks in the creek.
Fast forward three and a half decades. My brother was complaining to me the other day that my niece wants to hang out with one of her friends all the time and he and said friends parents just don't have time to arrange it all. It turns out her friend lives in the same neighborhood, a quarter mile away.
And I'm like "Why are you arranging anything? Why aren't they capable of coming and going as they please? She can get on her bike and ride there."
He looked at me like I'd proposed throwing his precious angel into a shark tank. Let her wander alone? Unsupervised? Just... out there?
It also turns out, by the way, that my niece is a poor cyclist because she isn't allowed out on her bike without my brother or his wife with her.
My brother and his wife are not unique in this. I have never, ever had a conversation with parents in my age cohort who aren't raising their kids far more restrictively than we ourselves were raised. Everything is monitored. You call them out on it and the near-universal response is "It just isn't safe out there."
Now, my niece and nephew are a bit younger than teens... but with teens it gets even worse, because then their parents are still paranoid about what could happen to them, but also suspicious about what their kids will use their new teen bodies and brains to do to THEMSELVES or to others.
I wonder what percentage of the parents in that survey would be willing to, if their kids asked for the car keys to go hang out with their friends, would hand them over without a down-to-the-second itinerary, a precise list of who will be present, and a stern admonishment that they can track the car on GPS so watch out, mister. I wonder that very much.
Teens have limited agency. They have no money and their lives are controlled. You want to know why they're not doing something? Probably because their parents don't want it done.
And all this is without even getting into "maybe they're hanging out online. Why is being on a group video call in Discord talking about nothing in particular for three hours considered more problematic than hanging out at the mall talking about nothing in particular for three hours?"
(Both my local malls ban unescorted teens, by the way.)