Happens far more than you think. It can be an innocent (sort of) mistake, where authors see the citation in a previous paper and simply copy it into their own.
This feels like something that would, at large scale, be unhealthy for science as a whole. While existing papers have already gone through their own quality checks, this enables bad, misleading, or false statements to propagate which can end up being a blow to the credibility of the entire model. Shouldn't there be an ethical duty to due one's due diligence?
There's a crowd who tilt the other way -- if I might possibly have hinted at the idea before you then it's borderline malpractice to not reference me. In many fields it's common to directly reference what appear to be the bigger transitive references then, even if they didn't directly influence this work in particular. I'd personally want to see a twidge more evidence before bringing out the pitchforks.
Funny. I read your previous comment (with the ?! ending) as sarcastic. Now I see you were serious. I would be astonished if most authors have actually read even a fraction of the sources they cite.
