DEAR ABBY: I have an answer for a question from “Excluded in the East” you printed on Sept. 24: “Why do married couples exclude single people?” As a single mother with three children for 15 years, I made the conscious decision to conduct myself as I always had when I was part of a couple. I hosted backyard parties and holiday dinners and invited my married friends. I initiated invitations for dinner and a movie. At restaurants, I made sure to pick up my own tab. If a couple insisted on paying for my meal, I insisted on paying the tip ...