[cellaris]

Synchronisation is not only for reading positions but also for bookmarks, underlining and notes. You can remember your reading position using your memory or any other method you prefer, but anything you underline on a Kobo Libra 2 will not appear underlined on a Kobo Sage unless it is synchronised. Of course, you can also underline it again using your memory or choose not to underline it again. However, synchronisation is useful and convenient for those who have several e-readers of the same brand. Kobo also offers this feature for books purchased from its store and downloaded directly to the e-reader (Kepub format). If you use the ePub format, you cannot synchronise even if you purchase it from the Kobo store. The same applies if you use content from outside the Kobo store (both ePub and Kepub).

Is it important that Kobo lacks a synchronisation option for external content that is present in virtually every other brand? I honestly don't think so. But not because of what you are saying here, but because I believe that Kobo users behave in the same way as Kindle users: they buy their books from the Kobo store, download them directly to their e-reader and read them. Therefore, synchronisation will be available to them. I think those who load external content onto their e-readers are in the minority (piracy aside). And that is precisely why (and, to some extent, returning to the thread) I believe that Kindle is not in decline because Kindle users are oblivious to most of the concerns that are of such interest in this and other forums (DRM, backups, book editing, e-book format, side loading, etc.). Kindle users buy their books on Amazon and download them directly to their e-readers, and read without any major concerns. That is something that has not changed. And right now, Amazon's ecosystem is unrivalled.

(Needless to say, by "Kindle users" I am referring to a generic type and not to anyone in particular).