Why, prayer almost certainly has psychological benefits, like being less gloomy and more hopeful about the thing you pray for, such as healing. Placebo effect etc.

So I am not sure what exactly this quote demonstrate? That widespread beliefs can be wrong? I would say, widespread beliefs are often wrong about how things work out in the world, but not wrong about the actual end effect delivered in the mind. A religous fisherman my logic this way I pray -> I get more fish -> I feel better. Instead it works out as I pray -> I feel better. The end effect is still the same. That is because if it would be like I pray -> I still feel the same, sooner or later they would find a way to rationalize stopping wasting time.

Of course it is a bit cynical to claim to that we do everything in the world ultimately only to generate warm fuzzies inside our own minds, but it does seem so, unfortunately.