I installed the Redirection plugin on my site purely because I needed to redirect from my old Jekyll-generated feed to the WordPress feed when I migrated over. /me engages “smug mode”
It used to be people used FeedBurner to provide an unchanging address for their feeds (and fix the many problems in various RSS/Atom implementations at the time). The idea was that it was independent from your blog software, so could be a fixed point of truth. All the site owner had to do was update the configuration whenever they switched software. Eventually FeedBurner was purchased by Google, went out of fashion, and people slowly forgot about it…
FeedBurner itself is – surprisingly – still running, and I bet a good proportion of the feeds linked to it still work – whether or not they’re still active. I know when I logged in last year there were a bunch of my own still merrily chugging away without any intervention. Many of my oldest subscriptions still seem to use it, too.