Eugene Volokh pointed out several years ago (“The Language Police”, 1/26/2003):
Language defined by changing usage is what some call a “grown order” — a judgment formed by millions of people, based on their senses of what is convenient and comfortable for them. (Free market economic decisions are another classic example of something that’s mostly a grown order.) Linguistic prescriptivism (dictionarymakers recording what they think should be the usage, not what is the usage), is a “made order” — a judgment of a small group of people selected for the purpose of rendering their judgment. Made orders are sometimes useful, for instance in the setting of technical standards. But as to language, I think the grown order approach is far more likely to yield a language that is genuinely responsive to users’ needs than the made order approach.
And Liberman adds:
[I should also mention that Eugene Volokh was mistaken about how most dictionary-makers see their role, when he wrote that they "[record] what they think should be the usage, not what is the usage”. While lexicographers try to distinguish older usage from recent usage, and standard usage from dialect usage, and formal usage from informal usage, they’re definitely in the business of describing rather than legislating. As a result, Robert Hartwell Fiske, in his screed The Dictionary of Disagreeable English, calls them “laxicographers”. ]