This article is quite old. You'll find more recent use cases/examples on the current HTML5 editor's draft (http://dev.w3.org/html5/spec/Overview.html). In its temporal context the author was right (fieldset/legend/abbr weren't that used) but fortunately times have changed a bit and things aren't as bad as he describes.

I must be one of the luck SOBs who learned proper HTML and web development first, having picked up this whole web fad just in the last year (took a long hiatus, my last web app before that was written in 2003.) I have html-generating macros and I use legend, label and abbr within fieldsets throughout my code base (though I usually forget they even exist until I see the generated code.)