[crazypyro]

Because people buy it without it being proven and proving anything related to cognitive ability is both difficult and expensive.

This makes doing studies on their effectiveness a neutral to losing scenario.

Either:

The nootropic works. Great, you probably spent a decent amount of money and... The results are still going to be hard to quantify and measure. It may not be good enough results to convince people who already weren't convinced. Might as well not do it and keep making money off people who buy it without scientific studies.

Or

The nootropic doesn't work. Shit. Bury the results and never publish or risk losing a money maker.

[permo-w]

this is all true for the producers/sellers of the nootropic, but what about anyone else?

[paulluuk]

Indeed, it seems to me that a paper proving that nootropics are either harmful or helpful would be quite publishable, which is (unfortunately?) what modern science is all about.