First of all, I've gotta say that I love this thread. I think most of us had that "Oh S***" moment when we started dispensing and realized how many people were on stimulants. Then you start down the rabbit hole of mental illnesses in general being a constellation of traits that were deemed a disorder, and eventually arrive thinking that it's all just made up.
However, in hindsight I think there are a couple of explanations for what you're seeing. First, you've simply gained perspective that you didn't have before. "Everyone" isn't on stimulants, you just happen to be near a college campus and most college students don't have hypertension. Therefore, your pharmacy dispenses predominantly amphetamine salts. Second, as culture changes and we become more open about mental health, more kids are being evaluated and diagnosed with ADHD, which results in more amphetamine salts in your pharmacy.
Edit: Also, whoever said "It's a culture", nailed it.