Lest you think this is an imaginary problem:

Out of curiosity, I looked at a bunch of dead feed URLs in my feed reader this afternoon, including a lot of the NPOs I follow that do humanitarian FOSS development or open data stuff, and found 20+ of them that have dead feeds not updated since 2013 or 2014.

For some, the project seems to be gone. For one, trying to visit the feed URL in a web browser redirects the user to the project's shiny new Medium account. Does that get any news to the feed reader, though? No, of course not.

But the best has to be the project who's original feed URL is dead, but whose site now boasts a top-level masthead link labeled "Blog" that connects to a feed at (I kid you not) domainname/blog-2/

Funny how all the people who voluntarily followed your feed two years ago didn't stop randomly one day, your look at your new Fad.js-based site, find your new feed at a different URL, and start following that, too, huh?