> BTW, I don't understand the use case of reading ebooks on a desktop or laptop instead of on a phone or tablet (or eink reader).

Unfortunately, not everyone has all the screens, and not all phone screens are big enough to read novels and such. I'd rather read a book in my bed on my laptop screen and take notes quickly rather than an older phone and try to write on its keyboard.

Also, e-ink readers' screen refresh rate prevents taking extensive notes on the books. You can underline just fine, but longer notes are a bit hard.

Last but not the least, comic books in CBZ/CBR format really begs for a quality color display, since colored comics is half the fun in the comics. :D