You nailed it right on the head. Dr. Edward Hallowell, in "Driven to Distraction: Recognizing and Coping with Attention Deficit Disorder", said (and I'm paraphrasing at best) that many non-ADHD simply need to 'snap out of it' and pay attention, which he likened to telling a visually-impaired person they simply need to squint harder.

Likewise, that would also be like saying people with depression simply need to put on a happy face, and those with anxiety should just take a deep breath and chill.

Nobody wants or chooses to live with such conditions - if it truly were as easy as some people think, then these conditions wouldn't exist in the first place.