Why has the medical community been slow to accept nootropics?

To add to what you said, pharmaceutical companies nowadays are trying to exploit the market for greatest profit by creating drugs aimed at rare conditions. These are often called orphan drugs.

One example of this is the drug ivacaftor, which costs up to $200,000 per year to treat a subset of cystic fibrosis patients.

Your last paragraph is good, and illustrates one of the reasons why truly novel drugs are relatively uncommon compared to reformulations of tried-and-true blockbuster drugs. A significant part of the largest pharma companies' budgets is spent on marketing--often those me-too drugs that are touted as being more effective than older drugs, when they are sometimes just a single enantiomer versus a racemic mixture, or a pro-drug that is converted in the body into the same compound.

I think part of the difficulty in prescribing a cognitive enhancer is what exactly is it enhancing, and how do we measure it? As far as I know, many of the clinical measures of intelligence are based on assessing whether someone is grossly impaired, not whether they're functioning at peak capacity. Intelligence is such a fluid concept. It becomes particularly difficult to ascertain when peak performance is based on a balance of stimulation versus inhibition; in my opinion, often only pretty significant imbalances are commonly detectable.

Brains develop in unusual ways, which is part of…