It is important because it does not confuse the reader; a strong, precise word choice makes things clear and vivid. A strong word choice can also invoke feelings you want readers to feel. For example, a specific word choice can make your readers feel angry, sad, or inspired.
<h3><em><u>A restaurant (sometimes known as a diner) is a place where cooked food is sold to the public, and where people sit down to eat it. It is also a place where people go to enjoy the time and to eat a meal. ... These restaurants serve fast food, that is, inexpensive food, prepared and served quickly.</u></em></h3>