Kids and teenagers need some time to do their own thing, so given that most of the "waking hours" are filled with school and other things that we effectively force on them, of course they try to steal some hours for themselves where they can.
In my case, it was programming 8 bit computers and yakking on the CB net a friend and I had setup. We had about 20 people on it at one point. Adults tuned in regularly to listen to us kids talk about all kinds of shit.
Amazingly, they left us alone.
One of the best things we adults can do for our kids, a lot of the time.
The other thing we can do is bring them a lot of hands on experiences. Doing stuff.
Both are high value.
I stayed up until 2 or 3 am reading books because I wasn’t tired. They’re staying up chatting with their friends because they’re not tired. The connection is the “not being tired.”
I get that there are a lot of valid cases where the answer is "homework", "circadian rhythms", "evolution", but...
80% of the answer here is electronics, and really just social media + smartphones. It's incredibly easy to stay up too late when you're hyperconnected and chatting with your classmates late into the night. It just wasn't even a possibility 20 years ago.