Who made up these rules?

Yesterday, my grandson, the eight-year-old, and I went to the library. As we were going in, he takes his cap off and says, I know that I am not supposed to wear my cap in the library. I say, that’s great that you know the rules of etiquette and he says, why? I say, because it is good to have manners and play by the rules, and he says, I know that but why do we have to take our hats off? I say, well, it’s a tradition, like the way we shake hands or the way we greet each other or keep our hair combed. Then he says, it’s silly and I say, yeah, it is silly. But, when we got off the elevator, he took his cap off and I held on to it while he sat in the chair and perused the book that he was going to check out.