Really? Where? Surely not in Europe, where the psychiatrist simply asks you a couple survey questions like "Do you have difficulty finishing tasks?", "Do you overanalyze things?" or "Do you frequently interrupt others in conversations?" before giving you a script for Concerta / Medikinet. The entire survey takes 5 minutes and if I was to take it seriously, then my entire family has ADHD including the dog.
One should draw a distinction between bad faith actors and good faith actors. For bad faith actors you are correct, but you could say the same thing about a lot of controlled substances. They (stimulants) are at least as controlled as benzos if not opiates. After all there is no objective test for chronic pain either from what I understand. For good faith actors I think there are perhaps the correct or at best too many burdens already, as given by the large percentage of people who are under-treated.
Everywhere in the EU. It's not like ADHD can be diagnosed with a blood test, so you are asked questions from a standardized survey and you get a script if you answer "yes" enough times.