The same way people write "citation needed" and then put their brains to sleep.

It's not as if they will then go to replicate and evaluate those citations (if they were, they could just as well try to evaluate what the other person told them directly, or at least try finding those citations for or against it themselves).

They just need some comforting assurances -- which will then repeat freely, few (or nobody) bothering to examine those "citations" at any step of the chain.

For me, unless the science is old enough to be including in University 101 courses, I don't much care about it. Unless you work in the field (and will actually use and evaluate the results mentioned in it) a peer reviewed paper is worth almost nothing to the casual HN reader.