It's just that they both fell out of fashion when social media decided they prefer to keep their users captive than accepting interop.
But many podcast clients actually still support Atom (probably using a feed library that supports various formats?) and basically all non-podcast feed readers support Atom.
I liked Atom's clean design but it felt it was mostly pushed by Google (I may be misremembering) and in the end the syndicated web faded into obscurity anyway.
And Dave Winer was strongly against ever clarifying the spec, and that’s part of what led to Atom.
There's really no good reason to use anything other than Atom.
