I don't know anything about Elm subscriptions yet. But there is a lot more to this stuff then just event emitters.

Things like:

* When an event/action/etc comes through, does it always call listeners synchronously? Can you change that and schedule events manually?

* How do you compose subscriptions/event handlers? This is usually the hardest part, and where simple event emitters really start breaking

* What about the lifecycle of the listener? What happens when it subscribes or unsubscribes? More importantly, what happens when the source that it subscribed to "shuts down"?

All of these things get pretty complicated and is the reason why various fields like FRP exist. Simple event emitters work immediately, yes, but they are a pretty terrible abstraction to build an app on.