There have been studies that taking it for 'cognitive enhancement' in people that don't actually have ADD/ADHD may actually be detrimental. If someone's performance is 'enhanced' by taking it, maybe they suffer from some baseline inattention and would benefit from the medication. I knew people in college that used it to stay awake during 'all nighters' prior to exams, but it didn't really seem to improve their performance.
Does Adderall Make You Smarter?
Adderall May Not Make You Smarter, But It Makes You Think You Are
"Interestingly, those who have the least ability in a particular area are likely to see the greatest drug-related improvement. In fact, on some tests of cognition, the smartest people actually showed performance reductions, a result that may address some of the concerns over “cheating”: on tasks involving working memory and impulsivity, stimulants had a leveling effect, allowing below-average performers to catch up to their peers, not dominate them. According to Farah, the typical student user is actually not the overachieving brainiac but a “white male frat brother with a B average.”