brushing? what's the point of that?

My puppy doesn't understand the purpose of a dog brush. The real purpose is (and i got this from wikipedia) "to groom a dog is helping to rid its skin and coat of any parasites and make the dog look pretty. I don't think Bentley saw that part. Because when I brushed his head the fur looked great and perfectly smooth until..... He shook himself. One quick shake and itch made him look like this!