Specifically the primary email address, which would typically be either a student or teacher email for the institution. Users can chose to show or hide their emails individually, while administrators can set the default and override for all users.
Currently there is a option to view the primary email address in the people tab in courses but it needs to be enabled. I would also argue that it is not a very intuitive place to look either.
Neither is the current method, which is that users would need to manually type their email in the biography filed in their profile. No one is going to bother doing that.
As for teachers, currently they can list their contact information on a page under the module tab. I certainly wouldn't think to look under "modules" for contact information.
Each account already as a primary email address associated with it, so having a simple option for it to be displayed on a user's profile is a small but useful and intuitive addition, for all users of canvas.