I'd guess it's simply that PG codes html the way he learned years ago. Not snark – you have to justify throwing out your table + spacer.gif knowledge to learn how to do things with div + css. Maybe he doesn't see a huge benefit. Also ( http://www.paulgraham.com/arc0.html ): Arc embodies a similarly unPC attitude to HTML. The predefined libraries just do everything with tables. Why? Because Arc is tuned for explorator…
i don't think there's anything inherently "wrong" with using tables. there's just a better way to do it. if you don't want to do it the better way, thats cool. it might negatively impact you (higher bandwidth costs, slower load time, etc.), but it probably won't.