@david_megginson how can people want that if they don't even know that's an option? Not many people know what an RSS/Atom feed even is.
Having them signaled directly in the browser would make people learn about RSS/Atom in general. Which in turn would perhaps lead people to question the apparent orthodoxy of following publications only on social media.
Which in turn could lead to a more healthy Web. Which is something Mozilla at least pretends to care about.