I've noticed its a common thing wherein:

1. People imagine without any evidence, but only a plausible story, that X is good for Y (say for instance, vitamin C for colds, because vitamin C is involved in the immune system)

2. Study after study is done finding no benefit, but each study you quote, someone finds some nit pick about it "well maybe the dosage wasn't high enough" or "maybe they did/didn't take it with calcium" and then continue to believe there must be some way to derive benefit