OK, let''s throw out all the rules of the English language. Hey, change is good, right? Who needs rules? Especially when it comes to standardized communication.
Me go school you not go talkie b'school we ok ok??.
Your example was clear and simple, which proves my point. Rules are helpful, but not necessary to convey meaning. Language needs to adapt. We all want language to be simple, but we also want to be expressive. Colloquial English, as per your example, helps define one's identity.
I'm not claiming that we should disregard "standardized communication." I am claiming that it's acceptable for style to win over economy or simplicity. How many prepositions or cases do we need? How many verb forms do we need? How many suffixes, prefixes, and irregularities can children take before they begin to simplify? What combinations of sounds are easily pronounced and easily understood? Can a 19th-century grammar be used in today's fast-paced and impatient world of immediate information?
Stylistic expression also plays a role in language adaptation. Although the story is apocryphal, some say that the distinct 'th' pronunciation of Castillian Spanish was due to courtiers imitating the lisp of the king. As a result, Castillian has more character. Idioms get added to language every day. Some become more integrated, while others decay. It's all part of a necessary evolution.
Us linguists are concerned with the structure of language and the rules used to form this structure. These rules constitute a "mental grammar" that is thought to be well-defined, though not identical, in every language. These mental grammars are not the grammars we learn in school, but the unconscious process where we decide whether a sentence is well-formed. The process is independent of meaning. We both know that, "Oh, Cyndi went to somewhere similar to a mall and did something similar to buying an outfit which resembles a bitchin one." is an ill-formed English sentence, though we can easily guess it's meaning. This is because of our innate "universal grammar" that supercedes individual words.