They are catering to it, they're making better use of whitespace.
What nobody wants (well, nobody sane anyway) on a wide screen monitor (which is almost all of us, except the cranky ones who are still using CRTs for some reason) is a website with zero margins that doesn't at least try to format the text as a column. Because that's guaranteed to cause fatigue when reading, and makes it hard for the reader to even find the next line when they're trying to read something with line breaks.
I don't visit websites to look at white space. My wide screen monitor is so I can have MANY windows to different . The real problem is so many web-devs open ONLY their own site on their monitor, and then stand back to view it, as if their visitors are only going to view their site and nothing else. I get it -- we don't want to look at a solid block of text, but so many web-devs are jumping aboard the "clean-look" idea that they're making fonts tiny so they have more space to layout pages like a text-book. Next they remove menu words and replacing them with icons -- "Ooo gee, it's like I work for Apple!" WTF. Why should stare boggled at a bunch of hieroglyphs when I could have actual words? On the flip side, other web-devs are scaling their formatted-for-phone pages up to giant fonts because they don't want to learn responsive techniques.
What is probably more necessary right now are operating system UIs that make better use of wide screens. We all kind of rejected the Ubuntu "Unity" approach although putting a dock there wasn't really bad. There's the NeXT approach too (which ironically predates widescreens, and was removed from successors to NEXTSTEP two or three years before widescreens became popular) where the dock *and the menu* are on opposite sides of the screen (https://upload.wikimedia.org/wikipedia/en/1/1d/NeXTSTEP_desktop.png).
We have a lot of pre-existing art to steal from, but unfortunately modern UX designers prefer to steal from Apple, who have not really done anything positive in UIs since maybe Mac OS X 10.2.
Apple -- sheesh. No mouse buttons -- I wouldn't touch Apple products with a 100ft pole. Their UI is meh, but their file manger absolutely stinks. Apple users use one app at a time (I'm old, so I know, I've been there, been watching the evolution of MacOS, Windows and many unixy desktop env's for 30+ years), and if a designer is striving to be Apple-like, then I pity them. Have you noticed that Thinkpads and (mostly) Latitudes have kept their mouse/trackpad remote buttons and avoided the "click-pad"? That's because that minimalist trend is for people with "de-cluttered" homes--like living in a hotel room--not with messy workshops where shit gets done!
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