When I was a kid, I would sneak out of my room at 3 in the morning to play Diablo. There's not a whole lot parents can do to police kids' online activities who have a burning need to do what they want to do despite parental involvement. At some point you're fighting a war using the most precious resources you have against an adversary that has an endless supply of them.
I did the same thing to grind levels in Runescape and I look back with regret, getting <4 hours of sleep during an important developmental stage in my life.
My parents didn't even suspect that I'd do such a thing. But they could've trivially stopped it. If they knew I was doing it, they would've removed the computer from the game room. Luckily for my kids, I know how addicting gaming can be unlike my parents did back then.
I don't really know what you're trying to say. Kids have almost zero resources. If they have an internet-connected device they can use 24/7, it's because you got them one and you let them.
Kids do have more disposable time than parents do, but that's also why kids are so good at creatively filling the void when they can't just turn on their dopamine machine. When I was bored at my grandma's house without electronics, that's when I learned to draw, a hobby I've taken into my 30s.
