I have been aware about Firefox's Reader View mode for some time but
never actually used. There are not much situations when the web site is
as unreadable as it requires such mode. It might be related to the
selection of web sites I am are visiting, though.
I also have a GPD Pocket mini-laptop which has the 7" screen
(1920x1080). I don't use it too much these days because there are no
reasons to travel. But I use it sometimes. Usually when I do not want
to turn on my POWER9 workstation. It is usually when I want to see
weather forecast, to check e-mail or read news (many such places -
including the News section of my employer internal website - are
overloaded by modern stuff so I have to use modern browser like the
Firefox to access them).
And then the Reader View is handy. It allows to easily read www pages
on such small screen. So I finally understand why this function is
available and why people like it.