I certainly agree that some (probably most?) web pages have way more UI logic than they need to present the information to the user. Loading animations, back-to-top buttons, fixed position headers, social-share bars, and so many more UI components are totally unnecessary.
However CSS does have an important place even in the most basic presentation of information: proper styling can vastly improve readability. Especially on mobile devices where the layout must change to fit the device and a fixed 800px is totally unacceptable. This adaptation to fit the device is what sets webpages apart from more rigidity constrained types of documents.
Also, there's some degree of artistic expression in a nicely designed webpage... It's beside the point of why extensive styling capabilities are "needed", but that's part of why they're so popular.
> Especially on mobile devices where the layout must change to fit the device and a fixed 800px is totally unacceptable.
Why? Why should "the layout ... fit the device" --
I'm not trying to fill the user's screen;
I don't want to fill the user's screen.
The smallest iPhone screen size I see
is 320 × 480 pixels. With the horizontal
scroll bars, the 320 pixels would be usable,
and if the Web browser would permit using
the 480 pixels for the 800 pixel width of my pages,
then that would be even better. Some of the
other iPhone resolutions are 750 × 1334,
1242 × 2208, and 1080 × 1920 pixels, and there my
pages 800 pixels wide should look nearly perfect.
What's the problem? I'm not seeing a problem?
I'm trying to learn. Where am I going wrong?
What am I not seeing?
> With the horizontal scroll bars, the 320 pixels would be usable
Try reading an article while operating a horizontal scrollbar... it's a horrible experience because every line requires you to scroll from left to right, and then back to the left.
Also, your 800px page will still have a horizontal scrollbar on those devices because they're rendered at 2-3x, making the effective pixel-width of an iPhone 300px-400px. They could just zoom out really far and then use a magnifying glass to read it... thanks to the high resolution that would be possible, but it still wouldn't be pleasant.
> I'm trying to learn. Where am I going wrong? What am I not seeing?
Try visiting your site on a smartphone, a TV, a tablet, etc... you'll see the issue.
However CSS does have an important place even in the most basic presentation of information: proper styling can vastly improve readability. Especially on mobile devices where the layout must change to fit the device and a fixed 800px is totally unacceptable. This adaptation to fit the device is what sets webpages apart from more rigidity constrained types of documents.
Also, there's some degree of artistic expression in a nicely designed webpage... It's beside the point of why extensive styling capabilities are "needed", but that's part of why they're so popular.