You make fast food sound very negative by the way you are asking your questions, but, since I like your frankness, I will answer your question honestly. I have four kids and we, as a family, including my husband, eat fast food at least twice a week because my husband and I are extremely busy with work, school, and raising four kids. We both come from the lower class where we know people who literally hide food in their room to keep other family members from eating it. We have seen people go hungry for a day or two. When we were little kids, eating fast food was equivalent to eating in a nice restaurant. We know fast food is not nutritious but we would rather have out kids eat than go hungry. Plus, a good majority of our busy schedule includes taking our kids to after school classes like karate, gymnastics, soccer, t-ball, basketball, and, soon, fencing. We keep them active to keep them from being over weight.
I know, I just went on and on but I felt your question needed more of an answer, or at least an honest one.