RSS and ATOM are both nearly always machine generated and machine read so this may seem trivial to argue, but for those who are interesting in seeing the difference, this is a good article http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared
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When I wrote a forum software a while back, it was trivial to not only add a feed for new threads but also for new comments (per thread and board-wide). Made it very easy to monitor updates on all my devices. Most wikis have RSS/ATOM feeds for recent changes which is a great power feature for admins.
Mastodon is atom-based, I believe. Early twitter supported RSS / ATOM feeds which arguably made it easier to follow hashtags or news accounts.
Another benefit of RSS/ATOM is that you can plug them into chatbots or use them to mirror content. I would love to see syndication come back to the spotlight!