The drug users you know nothing about are the ones who use ADHD drugs to get an edge, but who aren't stupid about it and keep their mouths shut.
They:
*Get their sleep
*Maintain good nutrient intake
*Maintain good study habits
*Exercise
And on top of this - they dose with ADHD stimulants to get an additional academic edge, but they don't talk about it.
None of us have any idea who this group of people is, or what proportion of competitive students in law/medicine/science are now dosing.
I know more than one practicing psychiatrist who believes that stimulants enhance cognition and focus in non-ADHD users, that long term stimulant use is safe and beneficial to regular people who are seeking enhanced focus and mental endurance, and who have no qualms about prescribing it for cognitive enhancement to non-ADHD people.
My strong suspicion is that the numbers are much higher than the data suggests, that we have entered an age of cognitive enhancement, like it or not, and there is no going back.