I saw a chart of the Perth metro area and which areas voted what. All the areas that voted 'yes' were right on the coast, where it cools down quicker, due to the Freo Doctor. Also, since those are mainly the well-off suburbs, I suspect they have the means to enjoy the beachfront suburb lifestyle as well.

Every other area were majority 'no' areas, getting more so the further away from the coast one got.