Earlier quoted context omitted.
You're all wrong wrt. the scientific consensus :). The current consensus is that the ability to concentrate for longer periods on all the bullshit our modern lives are throwing at us is a normally distributed trait in the population, and ADHD is an arbitrary cutoff on that distribution. See https://news.ycombinator.com/item?id=16090523 for details.
I'm not sure where I was off - having the ability to concentrate is different than using that ability, and many people are really in the latter group because of a lack of proper discipline and priorities but end up getting diagnosed all too easily as the former.
Also having the capacity to concentrate but refraining from using it is an active choice; people doing that won't be complaining that they can't focus.