Part of this (from what I understand) is that casting a wide net and offering treatment can be an incredible preventative for children. So long as you aren't by default shoveling meds into the patient or telling them something is wrong with them (thus making false-positives almost certainly destructive diagnoses), a lot can be gained by guiding people with ADHD towards treatments.

There is a staggering amount of progress and recovery to be made, or damage to be avoided, by diagnosing ADHD. I'm all for a wide net so long as people getting caught in it are treated properly on an individual basis.