I have a kindle paperwhite and I use it all the time. Do I prefer actual book? Yes, but I am also into convenience, and trying to limit myself from hording books. I still do buy physical books, but at least this way I don't have half of the house filled with them. This is also great when traveling, so I can travel light and carry on or one bag only. I don't use my kindle for manga though, only because it's hard to read that on there, because of the format and size.
I also don't care to read on my phone or tablet, phone because of bad eye sight, and tablet feels way too heavy after a short time of reading in my wrist/hands. Another thing is I can make the font larger and more readable for me. Also, it's so much easier to download fanfiction and put it on my kindle than it is for me to read it another way if I am not at home reading on my laptop. My kindle paperwhite is the 7th gen, and over 7 years old. I will replace it when it dies but not before lol.
I also found out that authors make more money on ebooks than they do physical copies, so that is something I keep in mine. I don't see physical books being replaced by e-readers ever though.