Well I have a static site generated with Astro that includes parts that still use dynamic react stuff, for example an interactive dashboard / slideshow kind of thing and interactive widgets. The data is baked into the static site but I still wanted the rich interactivity from react in certain places. It naturally grew from an Astro project that didn't need any react stuff, so it was a logical and simple step to add it in the few places it was needed.

I've got slideshows and interactive calculators and things and it all works fine without the islands, that's the thing. LLMs will just incorrectly pattern match "interactivity = React".