BTW, everything is separated before publishing. CSS is one file, reset CSS is in another, there is a HTML template etc. Easy maintenance off line, online and published does not matter. It is similar with dynamic publishing.
As for the inefficiency we all know HTTP requests are the biggest enemy. All my pages are exactly one request. With everything being minimized, gzipped and unused CSS selectors stripped I do not see how this can be more 'inefficient'.