Unrelated blog post: For a web app I recently designed a "favoriting/bookmarking" system that was requested by several people.

Only like two to three people used it for a while, before they left for other jobs.

Now no one uses it.

Just to give a point of view of someone who uses features like this on other sites, and genuinely likes this offering:

I routinely use favoriting/saving features of various websites. For example, I routinely save and reference saved posts here on HN. The reason is my bookmarks don't sync across browsers, and I routinely use different browsers for different things. Further, the browser bookmarks/favorites system in place is generally pretty bad. This is especially true on learning/educational sites. I see things like Playlists on YouTube, for example. I could bookmark individual videos, but instead, I can offload that to YouTube, and not have that mucking up by bookmarks.

It's the same reason I don't really rely on built-in password managers. They are useless if they are tied to a specific browser or a browser at all.

Agreed. I rarely use bookmarks, and when I do the only reason is to make the URL show up in omnibar suggestions faster. If I find content I really care about, I put it in my notes. Otherwise, if the content is interesting but not crucial, I use the site’s favoriting mechanism if available (GitHub stars mostly).