Grammar lays the groundwork for effective communication.
Grammatical errors come in many forms and all can easily confuse and obscure meaning. Some common errors are with sentence structure, subject/verb tense, punctuation, spelling, and other basic mechanics and parts of speech. Even something as simple as a misplaced comma can completely change the meaning of a sentence. For example: "Let's eat grandpa" vs. "Let's eat, grandpa."
Grammar makes written content more readable and in turn more interesting.
That's all I got, I hope this helps in some way or another! XP