I'd say one of the causes for over-medication is the lack of willingness of both parents and children to work on ways to succeed without use of medication. I have (fairly bad) ADHD and my doctor did give me medicine, but only half the light dosage of Strattera, which isn't a stimulant. Long story short, I ended up hating feeling comatose from the medicine so much I began to work through my ADHD by structuring my life…
Ritalin works by inhibiting the re-uptake of dopamine and norepinephrine.
Amphetamine (adderal) works on dopamine, norepinephrine and seratonin. Not only is it a re-uptake inhibitor, but it actually "reverses the polarity" on neuron vesicles, causing them to dump their loads.
For some with ADHD, strattera works just fine. For others, strattera will make them feel like a zombie (or do nothing at all), while as little as 5mg of amphetamine salts a day will be sufficient.
A lot of folks with ADHD do just fine without medication. And others struggle with the thought of taking "the easy way out" for decades, and end up with a shitload of additional problems - primarily in the self confidence zone. Some only need the medication to get things back on track, establish routines and so forth ... but others really do need it.
Chronically untreated ADHD is painful, debilitating, embarrassing, and so unnecessary.