They should be included, as it simply is a valid use-case which most likely will actually be used. However, there should be many more examples or good real-world use-cases. Lack of those concerns me.
However, having gotten used to having them, I can safely say I'll always feel hobbled to work in a language that doesn't have them, so I'm very much in favor of adding them to JS, whether or not this is the proposal that wins out over time.