Punctuation is conventional rather than scientific, and has evolved over time.
In the modern world punctuation is an important thing to get right in formal writing. Readers of formal writing interpret punctuation mistakes as a sign of poor education or carelessness, and in either case tend to discount the work's validity. Here Nuts and Bolts presents a brief treatment of the use and abuse of the major punctuation marks. Choices in punctuation can greatly affect meaning. You are generous, kind, thoughtful.