In the first sentence, a dress is not a dressing mean it is a type of clothing and not a condiment for food. A dress is a type of clothing that is worn, and hangs from the top of your shoulder (like a strap or small supporting fabric). Finally, casual cloths usually cover your entire shoulder and end at the elbow. Which is why it is written, one wears cloths with the shoulders because the writer assumes the type of normal clothing is the type most would buy at stores that only expose the hands, forearms, and from the neck or above.