The English language is definitely not a static one. Usage of English is constantly changing and new words, or ways of saying old words are created, and for the most part used widely across the United States. In fact, I would even describe myself as a Descriptive language user, mainly because when I speak, it is not in perfect written English, but rather in a more widely used, generic slang dialect. The reasons that people generally speak in a descriptive rather than a prescriptive manner is mainly because of the evolution of language, but also because of the widespread use of the descriptive language, and also based on politics, whether it is changed by politics or changes politics.
English as a language has been evolving ever since its creation. In fact, when English was first created, it was almost unrecognizable as English and wasn't even called English. Over time, different cultures and people influenced changes in the English language, bringing with them new words, and different ways to say the same word. This has happened so much that English has become a language filled with so many different cultures. And this has ended up with people speaking so much in a descriptive manner.
Descriptive language is the most widely used form of English in America. So widely used in fact that people who speak in a prescriptive way are often ridiculed as children, or looked upon as weird or outcasts in adulthood, as shown in David Foster Wallace's work Authority and American Usage,
“A SNOOTlet is a little kid who's wildly, precociously fluent in Standard Written English. Just about every class has a SNOOTlet, so I know you've seen them – these are the sorts of six-to-twelve year olds who use whom correctly and whose response to striking out in T-ball is to cry out “incalculably dreadful!” etc. The elementary-school SNOOTlet is one of the earliest identifiable species of academic...