Can't speak for Robert but the organizations I have set this up for would like to be able to forward to any email but for sure on the same domain email. Example, email comes in from client for Mr. Bob but Mr Bob is not a contact center agent.
The Agent wants to forward to Mr. Bob but can not, so replies to customer that Mr Bob can be reached at firstname.lastname@example.org.
Two things happened, customer is like why did I waste my time sending the first one if Bob would only give me his email and Bob is upset because he isn't in a customer facing role and doesn't want customers to have his email.
OK so hope that make sense.