As the development is mostly web driven nowadays, HTML/CSS/JavaScript is something that the most developers tend to already know and thus have crossed the first barriers of entry to this kind of development.
If you know both HTML and a proper UI toolkit, you'll see how insane it is to use HTML for anything else than marking up text. It's like launching a space shuttle to go to the supermarket around the corner instead of just walking. The only thing HTML has got going for it is how easy it is to show 'Hello World' on screen. Anything more complicated than that and it becomes a total horror show, especially compared to how easy to use and simple regular UI toolkits are.
I would argue the exact opposite is true for anything more complicated than 'hello world'
I do think that developers who have previously only worked with web tech have a distorted idea about native platforms though. I spent my whole career working on the web, intimidated by the complexity of native apps. It turned out that native UI toolkits really are very well suited to building native UIs with minimal effort!
As a native developer I have the exact opposite view. Web development is insanely complicated compared to native. It's a complete jungle of flavour-of-the-day frameworks all designed to make web-development somewhat workable (and all of them failing in some ways.
If you're building a website, you have little choice, but if you're actually building a desktop app it's totally insane to use web based UI.
There’s an irony that people who will drop whatever they’re doing to learn this week’s hot crazy brain-bending quasi-DSL JavaScript framework think that learning Swift is too hard and don’t want to have to learn something new.