Because my reading apps can do more than the website’s reader can. Because then I own the file and the website cannot simply take it down. Because of all the reasons I listed originally.
Basically - is this site selling itself as Bandcamp for books, which means ‘hardcore’ readers can discover new and interesting ‘indie’ books and do what they want with them in whatever format they want, or is it selling itself as a fancy reading app with animations and things (which imo appeals more to casual readers/children, and the giant font also gives off that impression)? It is trying to be both - or is clearly the latter but has been posted here as the former - and that seems conflicted. You simply can’t make me believe that I am MORE free by being locked into one reading app vs downloading a file! :)