Is the grammar of languages really important?

Since the primary purpose of language is communication, grammar is of paramount importance.

In his science fiction short story "A Sound of Thunder," Ray Bradbury illustrates the butterfly-effect, the effect of one change in nature that can alter all that happens afterwards. One of the changes effected as a result of the alteration of nature by the character Eckels is in the message of a sign in the office of Safari Tours from which he has departed. For, when Eckels returns to the office, he is now unable read a word of this sign because the language has developed differently.
This sign exemplifies the point that unless there is a standard for a language, a grammar that is adhered to, this language can become so altered that communication will be destroyed. Certainly, without a standardized grammar for languages, it would become impossible for someone to learn a new language.

Knowledge of acceptable standards for a language aid in effective communication. In English the mere misplacement of a comma can effect ridiculous results: 

Yes, I ate Aunt Rita rather than Yes, I ate, Aunt Rita 

Thus, meaning is changed with punctuation. Certainly, the misplacement and dangling of modifiers causes problems, too. Often they are detectable, but sometimes, the reader is uncertain of the writer's precise meaning. Consider these two sentences:

David has only art class on Monday. David has art class only on Monday.

There is clearly a difference in the two sentences' meanings because of the different placement of the single word only.

While these examples are small errors, numerous grammatical errors in a written piece can confuse and frustrate readers. So, there is no question that a grammatically correct piece will receive more attention and a favorable opinion from readers, as well as communicate more effectively than otherwise. In fact, good grammar is so important to exact and effective communication that businesses nowadays are hiring companies that hold workshops for employees, which instruct them on how to more effectively write everything from memos to presentations.

The use of acceptable grammar creates an impression that a person is not only educated, but also intelligent. There is no question that a command of the grammar of one's language causes people to perceive the other person in a positive manner. Poor grammar skills not only make people think less of a person, they also annoy the reader or listener who must try to decipher what is meant. So, proper grammar creates a clarity of meaning and intent as well as an effectiveness in communication, three of the most important purposes of language.