Nothing really rouge about it. Google was big on RSS initially as a way to subscribe to content across the web. They had their own RSS Reader after all.
Yet, Chrome added an experimental "Follow" feature in 2021 for RSS subscriptions [1]. Edge did the same calling it "Follow Creators" that mostly focuses on YouTube but also uses RSS [2].
[1] https://blog.chromium.org/2021/05/an-experiment-in-helping-u...
[2] https://www.theverge.com/2022/1/17/22887626/microsoft-edge-y...
For instance, I dislike having to open YouTube to see what's new (or get notified by email) so I end up missing a lot of new videos from a handful of channels I consistently watch. Once I discovered there the RSS feed for videos, I added them to NetNewsWire on the Mac and it's been a much nicer way to see what's new.
So for people like me that would probably never watch new content, the RSS feed offers another way for YouTube to get me back on the site. That being said, I hope they don't kill it.
Handy if you parse that into something like SQLite and use that as input for something like `yt-dlp` for channels you want to follow but which are generally unwatchable "live" due to, e.g., a 15 minute video having a near-2 minute sponsor segment and 5 inserted ad-breaks.
Or if you only want certain uploads from a channel, e.g. "A Closer Look" from "Late Night With Seth Meyers", it's simple to filter the RSS and only watch/fetch those.
And it's how I use Lemmy now that I've switched over.
Youtube...that may be handy for. But I think the channels I follow regularly like that also publish as a podcast, and most of the time I'm fine with the audio-only versions.