This is something of a CS-specific problem, and is in part a side effect of the field's tradition of digital-first author-prepared publication. In basically any

This is something of a CS-specific problem, and is in part a side effect of the field's tradition of digital-first author-prepared publication. In basically any other academic field, any paper that is being passed around or linked to will have a header, footer, etc. that has its bibliographic details. And in fact, most/all CS papers _do_ have a "real" version _somewhere_ that has the date and other relevant info, but in CS, we have a bad habit of passing around links to a papers that point to a random version that the author posted somewhere, rather than to an entry in a proper bibliographic database or to the canonical/archival PDF of the paper. I.e., not the PDF that the author posted themselves somewhere (likely missing dates, publication information, revision history, etc.), but the version that came as part of the conference proceedings or journal that the paper was published in. Those typically (though admittedly not always, depending on the conference) have headers/footers added that include whatever would be needed to properly cite the paper. Google Scholar etc. try their best to link to the "right" place, but are often led astray and point at the "random early draft on the author's website" instead, which of course perpetuates the problem. Incidentally, helping avoid this situation is the sort of thing is at least nominally a big part of the "value add" that traditional journal publishers are supposed to be adding- keeping track of citation/bibliographic metadata, assigning and managing DOIs, ensuring that there's a standardized layout and production process that includes such information in PDFs, providing archival/canonical URLs for papers, etc. It's also an important part of what professional societies that have publishing arms (ACM, IEEE) and libraries (like the NLM and its PubMed/MEDLINE services) contribute.