The comma is a valuable, useful tool in a sentence because it helps the reader pause in the right places. The most important attribute of a ball player, is quick reflex actions. We laid out our music and snacks, and began to study. She was late for class, because her alarm clock was broken.
Commas help the reader to see the necessary separation between ideas within the sentence.
The game was over, but the crowd refused to leave. Because her alarm clock was broken, she was late for class. If you are ill, you ought to see a doctor. After. . . Although. . .