I know plenty of people buying and selling adderall on the streets, and it’s for recreational purposes. I don’t think insulin quite has that going against it.
Well, insulin doesn't have that going against it because you can just buy it from Walmart. It doesn't require any people on the street.
But the recreational use thing is huge indeed—the fact that adderall is so potent, desirable and dangerous is what earned it a spot on Schedule II. The reason why people are "treated like addicts" is because people think all addicts are the same.
There are different reasons to be addicted to a substance, and not all of them are bad. Say, if the substance legitimately helps you by making your brain function properly, as does ADHD treatment, it should be okay to be addicted. Who wouldn't be addicted to feeling like their brain is finally working properly?
But being addicted to a substance just because it feels good, with no regard for your personal safety or health (i.e. overdosing constantly) is reckless and dangerous, and this is what people think of when they think "addict". This is also, unfortunately, what comes to mind whenever one sees someone enjoying their ADHD medication.
They compare it to the enjoyment of someone who is well and truly fucking themselves with some neurotoxic substance like meth or cocaine—short-lived euphoria that goes away once the drug stops manufacturing good feelings for them, not true satisfaction with their self.
It's sad, really. Though I'm not surprised that people can't see the nuance.