Health Care and disease prevention fall in the category of enhancing and improving upon nature. Security is about fixing and finding someones mistakes and bandaging the ones which can't. Man did not build nature. After all, gods can't be expected to be perfect, that's why we build machines.
You can say the same thing about cities. The issue is the complexity of the issue and not the origin of the problem...
If a city had an obvious security gap, it would be the city developers and planners who would ultimately be responsible for fixing the problem (and perhaps even for making it). I think it's more a question of where to put the line of negligence in regard to security ethics.