As a fairly new user of Linux, i was initially overwhelmed by the choices available, and enthusiastically experimented with the various options. It would be fair to say, as a former Win and Mac user, that my perspective was one of pictures, as rightly or wrongly we're driven that way by commercial intent. It's a lot easier to get people interested if they like the pictures, and human nature aside, the 'others' have been keen to put as much or more into presentation, than they are good code. The same could also be said of some Linux window managers, but this isn't necessarily a bad thing, in what seems a global linux community intent towards saving as many commercial os users from pain and sufference. I'm all for different choices, but i don't think it's a coincidence that the most user friendly window managers are those that most emulate commercial counterparts.
I also think this is about learning curve. If a young game wielding tyro has cut his teeth on the Win paradigm, he or she may feel they have paid their dues, so to speak, and see a different paradigm as somehow going backwards, or on the more extreme end, an 'insult' of assumption that they'll have to learn all over again. Many people can also be inherently lazy, so the task of relearning is beyond them by choice, and apathy. Then there's cool, and the application of it in front of peers. Are the window managers 'cool?'
The right click menu wielding tribe might think so, as they operate gleefully within a minimalist environment, gleefully crying out with a roar of success as they minimize the impact on machine resources further. That's ok, and objectively, very sensible for those who enjoy that sort of thing, but for the average user, quite possibly boring, and perceived as intimidating.
There's little doubt KDE and Gnome propelled linux into the ordinary household box, and with the advent of Ubuntu, Suse, etc., the average win and mac driven user has never had it so good for a genuine, easy to use, linux alternative. But with the glut of window managers, many specific to a particular task or workflow, we're fighting the 'one pic per box' mentality so profitably engineered into the heads of Mr. and Mrs. Joe average, and all the little averages. That's hard to counter when profit is at stake, and recent developments within the sulfuric labyrinth of the big evil show there's no sign of that abating. So where to from here? Does linux as a community continue to innovate, offering many alternatives?. I hope so. but i also wonder if a 2 stage approach would be useful here. A common, or default 'face' to represent, as an identifiable brand, the linuxOS, with a secondary stage for users who wish to venture further and explore other faces, once they've tucked the slippers a little more comfortably under the tux desk.
Or, the variety of options available are presented as a feature of linux, and we do more work as a global community to move perceptions in another direction, possibly that of 'we've got a face for every occasion, not just one...'
Personally, i think the second approach would be a more successful tack in the long run, but in this age of 5 minute society, engineered to accept 'One face, One OS', i may well be in the minority.

Two roubles worth,

Alex.