This is one reason Wikipedia discourages using primary sources (i.e. individual studies) as references. Not that using secondary sources is perfect either, but you can "prove" almost anything by linking to studies as there are just so many of them. Do 1,000 studies on homeopathy and some of them will show a positive effect (even when done well, ignoring there are also many bad studies on these kind of topics).
- some of the cited studies did not claim what the citation said they did
- some of the cited studies did claim what the citation said they did, but the experimental results were far too weak to support these claims
- some of the cited studies had such weak experimental design, that it would be hard to conclude anything about the subject at hand