For example Google probably directly indexes by keyword. So “foo bar” probably searches the union of all “foo” and all “bar” pages for “foo bar”. But if the page changes since indexing, they will serve matches that aren’t actually matches. Or websites might game the indexer so that “foo bar” isn’t actually visible but it shows up on the Google search page.
Don't get me wrong, it's good those things are available to be searched still but I don't routinely need 10 year old data. It would be nice if they'd archive things older than a certain date and give you an alternate way to search those things.
Maybe I'm searching for something where the tech is 10 years old so I need that answer and Google's results say "No current results. (number) archived results available. Click here" and let you click to load the archived results the same way they do with omitted results.
I don't know this is just something I've been thinking about for a long time. Maybe it's stupid but I get so tired of scrolling through stackoverflow posts from the 2010s when I'm looking for an answer on a new version of a language I'm using.