Hooks definitely build a complex data structure. They don't actually run immediately/imperatively. Even `useEffect(callback, undefined)` (no defined dependencies) which gives the illusion that it runs "immediately" on every render is still an illusion of sorts and there's a complex scheduler apparatus feeding on the data structures under the hood that useEffect builds.

The data structures that Hooks build in React gets built in a strangely bound, somewhat liminal `this` space so it effectively "disappears" in JS. That's certainly not how I would have built it. You are right that I probably would have used something more like JS Promises, given the choice. But I didn't build React's Hook systems, I'm just an outside critic. I'm very happy to agree that use of `this` bound things is about as impure functionally as you get in JS. (That said, it is a very JS solution that predates React and gets to old debates of whether or not JS is truly "OO". Prototypical OO is a gray space between OO and functional paradigms.)

Hooks are never imperative, even in the most complex multi-hook components. They use and build data structures. Those data structures are mostly hidden from view and hard to inspect, but they exist.