Why do some people consider the sight of clothes that were left to dry on a clothesline an eyesore?

My mom left some wet clothes to dry on our balcony the other day, and the apartment manger came knocking at our door to tell us to never do it again, because its an eye sore and its rude. How is it an eyesore? I don't get it. All we hung up were shirts and towels. I tend to be a little dense when it comes to rules of society, so someone please explain.