Why People Wear Glasses

My son and I were reading a book, and in it was a picture of a dog reading. I asked him if dogs could read. He laughed and said no. The dog was wearing glasses and I asked him why he was wearing them. He said, "Because he likes to wear them." I tried another approach to get the answer I was wanted to hear, which was-"To see the words." So, I asked him why people where them. With confidence his answer was correct, he said, "Because dogs wear them."