(The funny thing is that, in modern browsers this is no longer true - you actually can use CSS to restructure table layouts now. But, the world has already moved on.)
Though there's a broader answer, which is that generally as web design has modernized, so too have ideas of "semantic" markup. Semantically, table is supposed to be used to display data. HTML which is used for its proper semantic purpose is easier for screen readers, improving accessibility, and easier for search crawlers to make sense of the content, improving SEO. So a lot of old HTML tricks fell out of use when HTML5 started becoming popular.