Why simple markup languages make sense
I'm a big fan of simple markup languages for writing web pages (or in fact any sort of document; it just happens that web sites are pretty much everything I write these days). Recently I figured out a good expression of why:
Simple markup languages are the same idea as high level programming languages: less make-work and more of what actually matters.
(And as an added bonus, less interruption of my writing to sprinkle HTML all over.)
Languages like C and Java have a bunch of necessary repetitive tedium that you wind up doing over and over again to pacify the language, to the extent that automating many of them is a major IDE industry. One way that good high level languages are such a pleasure to program in is that they do away with all of this tedium and let you think about your program, instead of yet another set of canned getter and setter methods.
Simple markup languages versus HTML have the sample effect: less <p>s and <a href="...">s and more of your actual writing. At least for me, this results in a better focus on just writing, and thus better writing (and more of it).
As far as I'm concerned, one of the big wins of wikis is how they streamline writing for the web by using simple markup languages. (Of course they then often throw away a bunch of this advantage because browsers make bad editors.)
(You can argue that the real answer is 'get a good HTML editor'. One of the reasons I think that this is not a real answer is that the more streamlined and unobtrusive the editor is in adding HTML to your plain writing, the more what you write looks like a simple markup language to start with.)