I don't know why more people don't just use tiling window managers. It's a bit confusing at first but now I couldn't be happier. I used LXDE for a long time then realised - why don't I just use dwm to open stuff, and actually get a window manager that arranges my windows to maximise screen space usage?
"I don't know why more people don't just use tiling window managers. It's a bit confusing at first [...]"
That pretty much sums it up. I believe it's fair to say that casual users are (often) adverse to dramatical change--and switching from a point-click-and-move to a system that manages it all for you can be a bit crazy.
Well that's a problem with culture, I guess. Once you get used to a decent tiling WM (I'm using herbstluftwm at the moment), they're absolutely fantastic and useful. I think the experience easily competes with OSX, maybe not on ease of use, but definitely on usefulness once there's some investment.
It's like people using GUI applications for things when they really aren't necessary. I'm constantly helping out people who are using, for instance, the GitHub Git client (which is great), because it abstracts away the logic of using a system and creates more issues itself.
We're not really talking about average day-to-day users here, we're talking about technical people (like Linus Torvalds), so the ability to spend time investigating a new paradigm isn't unreasonable.