originally CSS had no layout facilities. (as it should be, see other comment). Layout was hacked in to css by abusing the "float" property into doing things it was never meant to be doing.
So if CSS wasn’t supposed to do layout, despite that being what people needed, and if you weren’t supposed to use tables for layouts despite that being what worked... then what on earth were you supposed to be using for layout? I don’t recall any other serious options out there.
Ideology trumped practicality and we’re stuck with the consequences.
or another way of putting it is they viewed web browsers as something more like a feed reader/news reader. that the browser and user should have control of how the information is presented, not the individual websites, which should stick to plain vanilla semantic markup with no fancy stuff. CSS was only created to stop people mucking up documents with <font> <center> <marquee> and <blink> which have no semantic value.
for a time mozilla had xul, but that was never an option for website layout.
And that's the heart of my frustration. w3c designs things, not based on what people need, or even what people want, but instead what they think people should be doing. So many problems of the web stem from the fact that the committee who's supposed to be directing the design of web technologies, has no interest in how people actually use the web. That creates a power vacuum which gets filled by browser manufacturers, who at least have an interest in the people using the web's needs.
The first web pages I wrote had no style information at all. And the first browsers I used allowed (and expected) you to define the default colours and fonts for pages to your own taste.
I am still a fan of minimal styling. It would save me a lot of time to write "style = article" on my pages and be done with it... but most people want their pages to look unique and exactly as they think it should.