The first edition of the book was published in February, 1876 by U.S. Army Major Henry Martyn Robert (1837–1923); its procedures were loosely modeled after those used in the United States House of Representatives. Major Robert wrote the book after presiding over a church meeting and discovering that delegates from different areas of the country did not agree about proper procedure.
Also, it isn't true that the rules hardly ever change. One major change was introduced in one of the recent editions was the concept of the "friendly amendment." (At least that's what it's called colloquially; I'm not sure the same terminology is used in the official manual.) When an amendment is proposed, the chair asks the person who made the original motion whether it is a "friendly amendment," in other words, does he consent to the amendment? If he answers "yes" then the motion is amended, and there is no debate or vote on the amendment separately. If he answers "no" then debate continues as under the old rules.
This procedure really threw me for a loop the first time I saw it used, but I have to admit, it saves time, especially when people introduce motions that they haven't completely thought through.
And this isn't some obscure rule that is applied only once in a blue moon. It happens all the time.
Sorry for the thread drift. (Or am I out of order?)