I think the context that some other responders are missing is that in some functional languages, like Elixir, streams and iterators are used idiomatically to do staged transforms of data without necessitating accumulation at each step.

They are those languages versions of goroutines, and JavaScript doesn’t have one. Generators sort of, but people don’t use them much, and they don’t compose them with each other.

So if we are going to fix Streams, an implementation that is tuned only for IO-bound workflows at the expense of transform workflows would be a lost opportunity.