Let's continue with the Google Ngrams example. All I had to do was search Google Scholar for "Google Ngrams" to find easy examples on the first page of results, like this one: http://www.aclweb.org/anthology/W14-1611
The paper is written by famous Stanford researchers, and they do not cite a single author of their data. Just URLs in footnotes.
This also happens to my research (ConceptNet) all the time. The fact that you haven't noticed it doesn't mean I'm making it up.
I don't see why you think researchers not giving credit for data is a different topic from what I brought up. What I said was, researchers in my field are in the habit of not giving credit for data, and instead they have adopted the convention of using half-assed footnotes with URLs in them, which is not appropriate credit. I speculate that one reason for this habit is that data often comes from inconveniently non-academic sources and would look bad in the bibliography. The habit is so pervasive that authors remain in the habit even when a paper exists.