Why do we use plurals in writing?

why is it important to using punctuation and plurals in a person writing?

Correct grammar and punctuation is very important so that messages are not misunderstood. In many situations it is easy to understand what a person means even if their punctuation or spelling is bad. Occaisonally, poor punctuation, spelling or grammar can mean that a message can be interpreted to mean something other than intended. For example: "They're cars" means "They are cars", "Their cars" means the cars belong to someone or some people. Two different meanings that sound the same when said aloud. If you wrote "There cars" that would not make sense and there would need to be some punctuation ("There! Cars!" for example). Hope this helps.