I have always understood the expression "to speak the Queen's English" to mean that one is attempting to speak in manner above his or her social station. The Best English is the Queen's English and all other dialects and variations are lesser versions of that. In England, the social stratifications were very delineated and the people of one class could usually identify other classes by they way they spoke. The more formal and proper and educated the diction and syntax, the higher the class. It was typical of people to try to speak one step above their own, so as to appear higher on the social ladder. The nobility then were most attempting to speak the King's/Queen's English. I think that this attempt to use language to one's benefit is still alive and well today. We don't write with slang in our formal work, but our Facebook page is a different story.
I would have to say the strict adherence to the ideas and the mere presence of the Fowler's book "The King's English" is a bit outdated by modern standards. Part of this might be due to the nature of languages being something that represents life and vitality. Languages change over time and the notion of being able to specifically pinpoint and enforce how a language is meant to be spoken is antithetical to this idea. Additionally, I think that the outdated nature of the concept of "the King's English" or "the Queen's English" is enhanced by the globalization and technology that have helped to make English such a universally accepted language. Given how so many text or use technology as a means of communication, there is little to legislate this use. For example, when someones texts "C U L8tr," and uses it as part of their own lexicon, it shows that the manipulation of language has become common understanding and use as to the meaning of such a phrase. While it might cause the Fowlers to rotate at a very fast rate in their graves to see such a use of English (which might not even fit their standard conception of the language), it is something that has become a frequent and common part of the language.