It is wise, polite and a manifestation of good manners for presenters to spend a little time meeting audience members after the presentation. I can be quite irksome from the viewpoint of audience response, for somebody to present and then rush straight off to another appointment, with a selected host, or just to disappear altogether.
I believe the part of a presenter convincing listeners of the speech worth, comes from staying behind and rubbing shoulders with people in formally at the end of the session. I this helps to convince people of his or her interest in them. There is a certain “humanity” about following this line of action.