Why UIViewController is a subclass of UIResponder?

What's the purpose for making UIViewController a subclass of UIResponder? Was it done solely to pass the rotation events?

I could not find any definitive info on that in the docs.

Update

I understand that if something is made a UIResponder, this something is suppose to be included in the responder chain and process events. But I have two gnawing doubts.

1. As far as I know, UIViewController is put into the responder chain right after its view. Why do we need a view controller in the responder chain at all? Its view is already there, so why don't we let the view process the events that were not handled by its subviews?
2. OK, I'm ready to agree that we might need this. But I would like to see some real life examples, when processing events in a view controller is really needed and is the best/easiest/most appropriate way to do something.