The email feature is designed to make communicating with the people in your group easy. Roles and membership can change, and instead of having to maintain multiple lists of users and addresses, simply design mailing lists to include roles, and as you add people to your site, they will automatically be added to the members mailing list!
Do you need addresses for certain committees to communicate? You can do that too!
Do you need a list for the public to contact you? Public-facing lists can be used as a place for the public to reach out to you.