That's not really true, though. The viewer is the target audience of the display output, not the markup. The target of your markup is either someone technically minded (who would do a 'view source') or some sort of crawler that is trying to derive semantic sense from your document.
In that context, semantic markup makes total sense. Part of me is still disappointed that using XML+XSL for web pages never took off- implementation nightmares aside, separating page data and page presentation is an awesome concept.