Something like a Kindle Paperwhite works, especially for people who read a lot of fiction. It's small, light, easy to read outside, and fairly cheap.But upsize it and now you have a very limited function tablet.

OK, it works for reading PDFs of things like scientific papers (which I understand is something people like the Remarkable tablet for). And it's easier to read outside. (Might be a bit cheaper too because you don't need as powerful a processor.) But you're mostly trading off a pretty general purpose device--which is getting even more so--for something that has a really narrow set of use cases. And isn't really as good as the smaller models for just reading text.