>So, shouldn't it be used by people who believe it works?
You can't ignore opportunity cost when evaluating value/ROI. It's not merely about the absolute benefit any given method/material provides, but about how that compares to whatever else might have been done instead. This stuff is very much not free (hence being a "billion dollar industry"), either in terms of money or time, so the only way it "should be used" is if there was no superior (cheaper, faster or both) way to induce the equivalent placebo effect, and no other way whatsoever to produce an actual effect beyond placebo. That seems highly doubtful, given proven benefits from other forms of actual study. With the time/money spent on this sort of pure-placebo "Brain Training" someone could have worked on learning another language for example, or invested in other valuable training.
The same argument you propose here is commonly applied to other highly profitable placebos pushed to the public, and in general the flaw in reasoning is always the same one of ignoring comparative ROI. Probably the most classic example would be homeopathy, wherein people literally just buy bottled water for hundreds to thousands of dollars per gallon. By definition there should be no negative effects, because there is nothing there but water (perhaps with a few flavors or non-bioactive aromatics), so worst case there is no harm, best case somebody experiences a bit of placebo benefit. That leads to "well what's the problem then, it can't hurt." But people don't have unlimited resources, any spending on pricey water directly subtracts from what they might have spent more productively elsewhere. Worse, choosing a non-medicine placebo may result in them failing to use actual medicine that was appropriate.
So it does matter when something like this is pure placebo. Perhaps most humanly, it matters because it's not what people were being advertised, signing up or working for. "We lied to them because it was good for them" does not cut it.
You can't ignore opportunity cost when evaluating value/ROI. It's not merely about the absolute benefit any given method/material provides, but about how that compares to whatever else might have been done instead. This stuff is very much not free (hence being a "billion dollar industry"), either in terms of money or time, so the only way it "should be used" is if there was no superior (cheaper, faster or both) way to induce the equivalent placebo effect, and no other way whatsoever to produce an actual effect beyond placebo. That seems highly doubtful, given proven benefits from other forms of actual study. With the time/money spent on this sort of pure-placebo "Brain Training" someone could have worked on learning another language for example, or invested in other valuable training.
The same argument you propose here is commonly applied to other highly profitable placebos pushed to the public, and in general the flaw in reasoning is always the same one of ignoring comparative ROI. Probably the most classic example would be homeopathy, wherein people literally just buy bottled water for hundreds to thousands of dollars per gallon. By definition there should be no negative effects, because there is nothing there but water (perhaps with a few flavors or non-bioactive aromatics), so worst case there is no harm, best case somebody experiences a bit of placebo benefit. That leads to "well what's the problem then, it can't hurt." But people don't have unlimited resources, any spending on pricey water directly subtracts from what they might have spent more productively elsewhere. Worse, choosing a non-medicine placebo may result in them failing to use actual medicine that was appropriate.
So it does matter when something like this is pure placebo. Perhaps most humanly, it matters because it's not what people were being advertised, signing up or working for. "We lied to them because it was good for them" does not cut it.