What we consider correct or proper English has long been bound up in class distinctions. Prior to the advent of public education, this was much more obvious than it is now. Proper English defined itself as the English used by proper people. “Real” English was the English of aristocrats, thus the phrase “The Queen's English,” which is still with us today.
But even in the supposedly classless or at least socially mobile U.S., we tend to attribute correctness to the social “winners”: educated, urban, northerners, preferably those from “old money.”
Inside academics, we trust organizations like the Modern Languages Association and the American Psychological Association to settle disputes regarding correctness. But few actual language users worry too much about such niceties when expressing themselves in everyday speech; the words of those with whom they work and play, the English of one's ethnic group, the English of those one wants to impress, are all far more important than those required in the classroom or spouting forth from TV talking heads.
These Englishes push back against the authority that comes with social class, and are therefore chaotic and a bit difficult to track, causing no end of trouble for those whose professions or ideals make them bound to advocate a certain set of standards.
But in my mind, this is as it should be: language is a tool best built as it's used, and the more aware we are of how we're using it, the keener our expressions will become.
Now, if only we listened as well as we talk . . .