Why it matters
Search engines and AI assistants favour recent, dated content: pages cited in AI answers are measurably fresher than the average Google result. An article with no machine-readable date looks undated, one last touched years ago looks stale, and a modified date earlier than the published one is a contradiction.
How to fix it
Put datePublished and dateModified in the Article markup (or article:published_time and article:modified_time meta tags), keep them true, and update dateModified only when the content really changes.