Do people give any indication of why they don't race? Do they sail fairly frequently even though they don't race? Do some perhaps feel intimidated by the idea of racing and concerned that they might be embarrassed if they perform poorly?

Your comment on the other thread about coaching may be relevant. Perhaps just having a session where you do some training drills on the water and/or some low key, fun practice races in conjunction with some social/family event might help people see the connection between racing and the social aspect of sailing.