Earlier quoted context omitted.
http://etoileos.com/etoile/ http://fluxbox.org/screenshots/ http://awesome.naquadah.org/ http://www.nongnu.org/ratpoison/ http://www.enlightenment.org/ss/ http://windowmaker.org/
etoileos - last news update 2012 and wasn't even about the project fluxbox - active and kind've interesting awesome - more of just a WM than full DE ratpoison - ditto enlightenment - okay, kind've resembles Win 95 too... but more of a DE than the others you listed windowmaker - been around forever; hasn't really "innovated" in forever; just a NeXT clone if I remember correctly for GNUStep I think my point stands. I w…
>enlightenment - okay, kind've resembles Win 95 too... but more of a DE than the others you listed
> etoileos - last news update 2012 and wasn't even about the project
What you seem to be missing is that these projects died because people thought they were weird, which is to say, innovation in the DE space pays negative rent, and that's no good, especially not from the perspective of an open-source project, which, the social dynamics of open-source dictate that projects need to acquire a large userbase to sustain an active development community for more than a couple years, that is to say, to make people keep working on it after the "new project smell" wears off.
In other words your observation is a direct consequence of the choices in DE that users have made and continue to make.
The recent trend has been towards modularity, and while you dismiss awesome and ratpoison, a major boon of LXDE et al is that, unlike Windows 95, you can replace the window manager with xmonad and still use all of the other components of LXDE. Modularity brings innovation to the people who want it while satisfying the large majority of users who apparently do not.
There's no reason for LXDE to ship anything but Openbox; LXDE could certainly switch to xmonad tomorrow, but their users wouldn't be happy. And who wants that?