There are lots of good arguments already about why templating is still useful despite CSS. I haven't seen the simplest, most direct, and one of the most important reasons said...

CSS controls how a section of a page looks, and where those sections go. It doesn't separate the content into those sections. I can use CSS to make a paragraph pretty, to put a sidebar down the right of my page, and to make my header big and bold in a pretty color. I can't use it to divide the content into multiple <p> tags, to assign the main content to the main page body and its sidebar info into my sidebar. That's templating work.

Specifically, before the last redesign of my website, I had a CGI that grabbed a story from a file, a sidebar from a different file, picked the interesting facts at the bottom of the sidebar randomly from a set of other files, and displayed it all using HTML and CSS. Next time I redesign, it'll be mostly static pages, but still generated through a template system (and probably a database for content next time instead of flat files).

Update: Fixed a spelling error and an accidental StudlyCaps usage.

Really late update (2008-09-25): added code tags around the <p> tag to fix the markup.