No accounting for taste, I suppose. Writing JSX is a nightmare to me. It's like we've forgotten 20 years worth of hard-earned knowledge about the value of separation of concerns.
You want things edited together to be closer in code also. A single file or couple of files next to each other that decide structure, behaviour and view of a component is better than few CSS/JS for whole site.
No. We haven't. Because there's a different separation of concerns: https://twitter.com/simonswiss/status/1664736786671869952