"It's called too much television!"
No, it isn't. Do normal children get out of bed in the middle of night and go the living room and sit on the couch cross-legged rocking forward and back for hours? And I wasn't watching TV. We only had a B&W TV when I was a child and the two available english language stations had little programming of interest to a child. That's just one little example of ADHD behaviour, one that I exhibited as a young child.
Now, whether it is really a disorder or disability or whatever is highly debatable. I personally believe it is just part of the spectrum of normal human psychology. It has its good side and its bad side. It's not a great benefit in doing software QA test engineering, like I do, but I manage. Fortuantely my innate intelligence makes up somewhat for my lack of organization and focus.
Your example is not typical of what is normally "diagnosed" as ADD/ADHD. We do not have millions of children getting up in the middle of the night and rocking back and forth for hours.