Don't need to. Look at the workspace of an experienced Mac user (who's using a large-ish display) and you will see that there are almost no maximized apps, and that plenty of different apps share the screenspace at once.
Beginner users (and non-Macheads) hate it, but I've yet to meet a switcher than didn't like it in the end.
It's a matter of paradigms - Windows doesn't really have a lot of inter-app interactions via the default UI, so there's no real need for multiple apps to be visit at once.
I switched to OS X four months ago, and while I think it's a great step forward from Windows, it isn't quite the same as a comprehensive tiling manager. I've used xmonad, and it's a dream -- I just haven't made sufficient time to put up the headache of installing it.
Taking two windows, tiling them side-by-side and maximizing them should be effortless. It shouldn't take a fancy hardware set up nor an expensive investment, and it shouldn't be hassle to install. There's no reason UI widgets I don't need should consume precious real estate when I don't need them.
I keep a copy of the dwm source (with a few relatively inconsequential patches) in the same git repository as my home directory. It's much less trouble to set up, once you get it configured. (I don't really care for Haskell, though.)
I'm a reasonably experienced Mac User - and I have no idea how to tile my windows. Can't find a utility to manage windows. No way in OS X to do it cleanly. It continues to be the most annoying element of my Macintosh experience - particularly as there a number of great tools in Microsoft Windows (http://www.codinghorror.com/blog/archives/000928.html) - and don't even get me started on the wealth of WM available for Linux.....
Interesting to be reminded of this. I switched a few months back, and it really was a bit painful. I found it hard to concentrate when I could not maximize, and I spent some time trying to find some software that would solve this. By now I had totally forgotten I experienced it as a problem at first.
it is not so much about screen real estate as much as jumping from window to window without a mouse. dwm + vim + vimperator = most productive environment. It is very natural to switch between programs all using the same key bindings.
It is amazing, well not really when you think about it, how much faster you become when you dont have to keep moving your hand(s) off the keyboard.
