I'm sorry your text is grey; this is a valid question. These are preliminary studies: someone says, "Let me try something," it appears to work, and they report

I'm sorry your text is grey; this is a valid question. These are preliminary studies: someone says, "Let me try something," it appears to work, and they report what they saw, with the resources they had. As a result, someone organizes follow-on studies with more resources, which costs much more. At that point, the effect usually disappears, due to the greater power of the more careful study.