And I don't know where you've been for the last 30 some years, but the web is not a text only format, and the reason HTML was invented was specifically to be able to create a designed space where text can actually make sense and is not a gigantic wall of impossibly small black on white text.
Yet the market for text only novels is staggering.
While you do have some going to that extreme, I think it's mostly pushback against the insane amount of bloat and overbusy design out there. Some CSS can be useful, to improve readability and offer a little visual appeal. But I think maybe you missed my point.
Traditional books are typeset the way they are for a reason. No or minimal pictures. Block after block of text, broken up and spaced for readability, comprehensibility, and flow. Different types of books are laid out differently, but they mostly follow this theme. It's highly effective.
You kind of broadly have 3* categories of web pages on the web, as relates back to print:
* Book-types (mostly text in nature) * Magazine-types (more about graphic design, with content mixed in) * Advertisement flyer-types (sales pitches, mostly about design)
These are going to have different design requirements. There's plenty to write on the subject of design for these categories, but in the interest of getting to the point: there's an awful lot of the first category on the internet, and it really requires very little in the way of CSS. It certainly doesn't require hero images and 10MB of javascript. Blogs should read like newspaper articles, technical content should be typeset with similar minimalism to technical papers or books.
* There's a fourth category: webapps. My personal stance is that these don't belong on the web at all, but given that they're going to be, they obviously have far different design requirements, and are quite outside the scope of this discussion.