An app using event sourcing does not need to be consuming events from an external messaging service nor does it need to be publishing messages to one. It could

An app using event sourcing does not need to be consuming events from an external messaging service nor does it need to be publishing messages to one. It could very well be receiving requests over a synchronous REST API from an HTML/JS UI. I believe the point OP is trying to make, is that integration with a messaging service/queue is a separate concern from what event sourcing solves but that the internal event pipeline often looks very similar to a networked one and so the two solutions are conflated.