>>38 i believe HTML 4.01 is used for aesthetic reasons, as a kind of subtle revolt against modern web. it's a somewhat popular thing to do, of course it's in part nostalgia, part creative restriction, but it also has technical merit: the result works in a really large variety of text browsers, reduced functionality browsers, retro machine browsers, accessible browsers, etc.
accessible browsers
You realize that the HTML5 standard introduces a lot of semantic tags specifically designed to aid accessibility tools interpreting web pages?
E. g. <nav> advises screen readers to omit the content of this tag in the initial rendering of the page to offer it later for further navigation etc.
I guess older versions of CSS are creative restriction but HTML5 really only removes old, unnecessary stuff like <blink> <marquee> and introduces more semantic tags like <section> <main> which have no special functionality other than indicate the type of their contents.