Even though there are ways around the fatty and sweet unhealthy foods at these fast food joints, generally speaking fast food is considered bad because of the number of unhealthy items compared to the number of healthy items. Most of the foods are heavy with calories, fat, and sugar. Also, most of these items are cheaper than the healthier items and they are more readily available.
The fruit and some of the salads have to be refrigerated and contain many different ingredients. They cost a lot more. Typically, the unhealthy foods are quicker to make and those foods are more frequently advertised than the healthy food items. When you look at the pictures of the food shown on the menus or windows of these restaurants, rarely are they the healthy salads.