Some trade associations offer free email as a membership benefit and as a way of promoting the organization. Some of the non-profits I'm involved with do it as a way to keep in touch with their members. They give each member an email address (which the member can forward to their own "real" address if they choose) and then it's a simple matter of sending one email to "members@yourdomain.com" in order to communicate via association maintained lists.

I think it's more of a "value-added" type of thing.