Lightweight OS's are becoming pretty popular, from what I know.
(from DistroWatch, in the beginning of 2011:)
"Looking through the tables, an interesting thing is the rise of
distributions that use the lightweight, but full-featured LXDE desktop or the
Openbox window manager. As an example, Lubuntu now comfortably beats Kubuntu
in terms of page hits, while CrunchBang Linux, a lightweight distribution
with Openbox is still in the top 25 even though it failed to produce a stable
release for well over a year. Many other distributions started offering
LXDE-based editions of their products, further contributing to the dramatic
rise in popularity of this relatively new desktop environment."
I suppose many people still have old computers around, that they can use, and
also make the same type of reasoning as I do, even for new computers, and
just decide that they don't need all the extra fancy features that other,
more heavyweight, OS's have.
I've even installed Xfce on a laptop bought only 2 years ago, because there's
simply no need for anything more than that, for everyone who uses such
computer, to do everything they need, and it's a much more simple DE to use
than GNOME, with the shell and all that, that it could run, with no problems.