The problem is that even that hyperfocusing is not always helpful. Focusing on something for 10 hours straight while ignoring everything else - obligations, one's body's needs, etc - is not very much healthier than not being able to stay focused.
(Not that I disagree with much of what you're saying; just feel it's necessary to point out, as many people do think the hyperfixating on things is strictly an advantage)
In my experience it often creates an unbearable internal conflict where you're acutely aware that you really need (or want) to do something else, but you find it impossible to set your current task aside.
I would end up in situations where I'm not enjoying the hyperfocus activity because I'm simultaneously feeling guilty over not doing the more important thing, and there's would be nothing I can do about it. I could try to switch tasks but my mind would wander back, I would make more mistakes, if I had to talk to someone then I wouldn't be present and alert in the conversation, and would suffer even more negative consequences because of that.
Nobody sees that side of it though.
It's called a "disorder" because it is maladaptive: it causes the individual to fail to adapt to the environment. Children and even adults with "attention deficit" often fail to adapt to school, leading to diagnosis. Plenty of teachers get fed up with impulsive children that are incapable of paying attention or even sitting still in class, and they send them to doctors in order to "fix" the kid so they can do their jobs.
It's somewhat self-contradictory though. When you look closer at these patients with "attention deficit", you find that a high number of them are capable of hyperfocus. There's almost always something that deeply engages them. For some it's computers, for others it's car engines, there's always something. You find that all these people with "attention deficit" can suddenly display the ability to pay attention to specific things for ten hours straight.
I make it a point to identify instances where the person is capable of deeply concentrating. I always try to disprove their notions that they are "dumb lazy kids". For me it's a matter of basic human dignity. Once that's out of the way, I may offer them drugs to help them cope with the environment they find themselves in. Not before.
Maybe the problem is just that these people are not compatible with the mass education system where you listen to lectures for hours on end. Maybe that's just the most efficient method for the school, not the best teaching method for these kids. Perhaps there is an environment where they are well adapted, where the disorder does not manifest. Until such an environment is found, drugs and therapy are available.