It probably doesn't cost them much to keep the RSS feed going, and it's a way to keep a subset of people coming back to watch videos that otherwise wouldn't.

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.

It very likely costs a bit if you think of it like a bean counter, in terms of "lost ad views." Though in fairness, if you're using RSS to browse Reddit, and you're not using an ad-blocker, you sound like you've all but gone out of your way to view their ads.

I would think the opposite -- YouTube makes most of their money from advertising on videos, so the driving goal is to get users to watch as many videos as possible. The algorithm they use is a big part of that, but RSS feeds are probably a pretty good way to get people who only watch a handful of channels back the site (as the RSS feeds are just links to the video pages, without video embeds).

That's a valid take. Though, not all videos are equally ad-ridden. I suspect if I were to start using rss to subscribe to channels I'd be favoring those that don't make much use of them. But yes, it's not so cut and dry.