Why should they? That document seems pretty legible, in fact, I would say its readability is excellent; specially in contrast to all those fancy fonts with #333 on #EEE that many "modern" websites use.

Further more, that page is responsive! and doesn't require 5mb of JavaScript and a high pref cpu to work.

I know your question was rhetorical but I'll answer it.

Its actually terrible to read on a wide monitor. If you were to give the content a max-width with some gutters its easier for your eyes to follow the lines. I always start reading a line that I just read! I'm talking about adding less than 10 lines of CSS, nothin major.

That's easier to fix. Just resize your window. Heck, if you use Firefox you can just press ctrl+alt+m for a mobile-like view without resizing the window.

Protip: You can resize the browser window.

And then resize it again when you switch to a different tab. Or I guess you could pop every tab out to its own window like it's 2003.

I'm writing this on a 21:9 monitor. Code on one side, documentation on the other.

It's puzzling that browser defaults are still so bad at this.

Annoying, but not puzzling. Nobody wants to break old sites that rely on the old defaults.

We C++ programmers spend enough time waiting for our compiler, we do not want to waste more downloading its documentation :)

But we do need more things to do while waiting for compilation to finish. In addition to making sandwiches, seeing movies, building pyramids, etc., I mean.

What's wrong with using compile time to play DnD?