Is that a disease, or a flaw in modern culture?
But is it true that "it’s too expensive to modify the kid’s environment" or simply that established powers make more money by "modifying the kid"?
Costs are relative, and I think the point remains that the kid's parents are relatively powerless to alter the kid's environment significantly enough to solve the adhd problem. Thus, the decision of the cost/benefit analysis of modifying the environment vs modifying the kid falls to the "established powers", also known as, collective society.
As long as everyone with significant influence is comfortable with the status quo, there's little pressure to search for other options, even if many parents might prefer another option.
If you read through any edition of the DSM, you'll find that most disorders in it are defined by symptoms being maladaptive in the subject's current actual environment, not by objective, context-independent criteria.
I was a "hyper" kid for a lot of my formative years, and didn't undergo medication for it, but wonder if it'd been even more pronounced with not quite as strict of a household regimen (I was fortunate in this regard - pretty routine home-cooking, balanced diet, occasional sugar treats but not a staple). A 2012 article I just quickly dredged up seems to note there's interest and some control studies possible for recommendations that don't deny the utility of medication, but seem to look for dietary conditions worth evaluation[1].
[1] http://www.oregonholisticcounseling.com/uploads/Kids_Nutriti...
I've always suspected I was and am still "hyper", because I have trouble focusing and always have to fidget or walk around the office. I just don't get up and run around like I did when I was 7. Even then, without meds, I managed to do pretty great in school and college, as well as my programming career. I've always wondered how much different I would've been had I taken ADHD/"focus" meds.
Not going to get good at guitar without focusing and practicing, if I'm honest. So, in a time when I would've been out riding my bike, I was concentrating on the instrument and tiring out my brain daily I think. Well, and the whole "don't do well in school don't get to play guitar" thing hanging over my head (for the best).
I kind of think I'd be, well, maybe a less creative person today because I like to let my mind wander. A person recently asked "How do you remember so much erratic & tangential information so fast?" and my only reply was thinking my brain is like a giant orb-spider-web-thingy that can fire stuff all around really fast and bring it back. I like to think my wandering mind made the most of spending time in the local library as a kid too - pick up book, read for a while, get another one, etc.
Obviously, this is just anecdotal, but my experience seemed similar enough to yours that I thought I might share a hypothetical answer to your question.
It is not only an issue of attentiveness, but ranter all executive functions. The poor naming of the disorder, and the observability of a persons focus, causes people to over emphasize the inattentiveness symptom.
If you are interested in understanding the reality of ADHD I'd suggest watching some of the talks by Dr. Russel Barkely.
Here: https://youtu.be/GR1IZJXc6d8
For a more complete talk: