Paul,
If you've ever read the history of the ground wire and how we progressed from ungrounded to grounded, the same rule applies: It would only be important in the event of a problem, therefore, proper trade practices installed by competent tradesmen mean those breakers are unnecessary. [Linked Image]
We don't count mice, heat, age, deteriation, etc.. You see, we didn't tell you, but in THIS country we have none of those problems. [Linked Image]