I literally discovered this site couple of hours ago form reading article that criticizes this approach lol
https://adamwathan.me/css-utility-classes-and-separation-of-...
We almost had a P2P semantic web. (Web 3.0)
Back then, pages were rendered on the server and in many cases there wasn't much templating either. People would normally have their sql query code, their business logic, and the html in the same function in a file >5k lines long.
Bsck then it made perfect sense. Now, considering everything else that's going on in Web development (JS explosion), perhaps not so much.