part of the problem was the semantic nature of the markup. Things that weren't tables would get marked up with <table> for layout purposes, meaning the reading-order would be all messed up. Or things that were bolded to indicate headings weren't properly marked up as <h1>…<h6> hieararchy heading tags, so screen-reader "show me the headings on this page" functionality didn't work.
There are scads of accessibility-features that raw HTML provides, but if you (generic-you, not picofarad-you) just bang things out so they *look* adequate but don't have the proper underlying structure, it throws away a lot of that built-in accessibility that HTML provides.
