Why are some cached pages on google search not there?

Sometimes during research you’ll find a page that is 404, but also won’t load from the google cache. Even though google obviously has a copy, since they include an excerpt with your search terms in it.

If google no longer has a cached copy, why does it even show up in the search?

Maybe the website author purposely excluded the page from being cached?

Then why does google have a cache link for it at all? Some pages don’t have cache links.

Not sure then. Do you have an example?

Yeah, I’ve seen some cached pages that didn’t look right, or were just empty, these past few years.

I think the Google cache was more reliable when pages were simpler: plain HTML with a little bit of CSS formatting and simple JavaScript.

Today a Web page is more like a program that executes in the context of the full Web site, with tables populated by databases and references to content management packages, etc. Google can only cache the files it has access to, and I doubt that it even stores all of those. So the results are less likely to be readable.