It's possible. We have plans to do so. There are a bunch of finicky corner cases, though. For example, destructuring will call the `return` method of the iterator when it's done (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...), so we have to be careful if somebody has defined `return` on the Array iterator prototype. You can supply a default value when destructuring, which is lazily evaluated, so we have to be careful about arbitrary side-effects taking place in the middle of the destructuring. We need to be able to fall back to something less optimized if we suddenly see a generator, or a user-written iterator. And so on.

Fundamentally, it's the same thing that impedes most optimizations: there are hundreds of different patterns we could optimize, it takes a fair bit of thought to get it right, and we have finite resources, so we have to pick and choose. This particular pattern turns out to be idiomatic in a lot of React code, which is why we're looking at it now. (Or so people tell me; most JS I write is gross little testcases.)