I wholeheartedly agree, and have written on this topic, in my book, and a few medium articles, including this one: https://dockruse.medium.com/trump-nose-best-4fdefbca82c1

I think that on top of the stigma (even within medical community) towards psychiatric problems, ADHD received particular confusion/fear/contempt because many of the symptoms of ADHD (rapid speech, fidgeting, jumping from topic to topic) look a lot like the effects of stimulant drugs on someone without ADHD. So pharmacists, or inpatient psychiatric hospitals, or prison medical staff are unwilling to provide medication that would actually help alleviate these symptoms.

Furthermore, mostly in response to the opioid epidemic, our governments at federal and state levels have added extra barriers and bureaucracies that make it more challenging to prescribe controlled substances like the stimulants.