This isn't some "bizarre fetish," it's an issue with implications from performance to code organization to legal compliance. (No, seriously -- Domino's had to deal with an ADA suit a few years ago because their app dispensed with standard elements with default behaviors, like <button>s, in favor of unlabeled <div>s that had effectively no compatibility with screen readers.)
This is a core component of a lot of problems with modern webdev.
Framework fatigue? Yeah, because UI toolkits frequently reimplement basic structural elements, in their own specific dialects.
Bloated codebase full of external dependencies, that only works well on fast internet connections? Well, look at all the overdependence on third-party libs, or even or even hand-rolled behaviors in JavaScript taking up dev time, for implementations of things that browsers support natively now.
Messy codebase that needs a CSS class for every element, or even style declarations within the CSS classes themselves? You can do less of that if you use semantic elements and modern language features -- because then you can write unique selectors without having to explicitly name everything.
I'm not saying that it's without its own problems -- obviously different orgs will require different levels of support for older browsers, for one thing -- but there's a reasonable argument to be made that the current ecosystem overcomplicates this a lot, and that relative to using the platform, sometimes all the extraneous dependencies are the half-baked alternatives.