I am (was) active in some smaller niche subs (certain crafts, mostly) and quite a lot of users in those subs didn't know what was going on. I guess some users only use Reddit for a few specific subs, and somehow manage not to see /r/all, etc.

Old Reddit on desktop, Apollo on iPhone and iPad, and Boost on Android. (Sync and Relay are great, but Boost feels most like Apollo to me.)