The grandparent post does make a point. If such a large proportion of the population has a 'condition' is it really a condition or perhaps just how we (as a species) are? Especially in the case of something that's psychiatric/psychological.
For example, I've heard estimates that around 10% of the population is homosexual and for many years people wanted to 'fix' them. Around 10%-12% of people are left-handed and (I believe) that historically this was also something that people tried to 'fix'. I doubt many of us think twice about these anymore.
To a sibling comment that suggested what if 1 in 5 boys were born deaf, I'd say that the world would be a vastly different place. So different that we may not even entertain such a question. If, instead, 1/5th of boys were beginning to be born deaf, there would be a medical emergency. Unfortunately, in the case of things like ADHD it's difficult to know if we've always been this way or if there's really been a change.
Normal vision could be interpreted as a range much larger than our arbitrary standard of "perfect", 20/20 vision.
Not being able to hold onto a thought for more than 3 minutes, or having to deal with potentially being distracted by every little thing that happens around me does not feel like the normal state of affairs. Trivial tasks can take me hours instead of minutes in some situations.
Unfortunately I'm currently in a country that doesn't allow me to get medication for this (and previously I was in a country that believes that ADD/ADHD magically disappears when you turn 18), but I still have good memories of how much it helped me get through middle school and high school (I went from almost never finishing my math homework to being able to finish everything in class in only half the allotted time).
What effort is being made to determine whether the etiology of ADHD is primarily biochemical (chemical/genetic), or primarily psychological (environmental/human-interaction)? Drugging to counteract ADHD symptoms makes sense only if it's the former.
Have boys changed, or has society?