@Geezer-Weasalopes - yes, supporting other stores is a good thing. For me, I've been using kindle since Amazon was the only ebook store besides (with a tiny selection) Sony, so it's the easiest choice for a DRM'd version.
But those all require already following them in some manner, yes.
Also yes to this. If you don't know they exist you might never find them. Hopefully as they add more volumes and titles Amazon and the rest will suggest the books to readers.