I only partly agree. I have two children. We are loving parents and provide them with a stable house, lots of food, plenty of attention. They have friends, toys, games, books, musical instruments, bikes, and a whole neighborhood to explore. We are an extremely typical middle-class household.
But left to their own devices, they will happily spend every waking hour in front a screen, watching videos or playing video games. There most certainly _is_ something incredibly mentally addicting about passive content consumption. It doesn't need a root cause, just like you don't need one with alcohol and other substance addiction.
(And because this is HN, I am obliged to point out that I'm not saying media addiction can't be triggered by some other factor. Only that a trigger is not required to cause the addiction.)