@SarahGen-- Like the article mentioned, as cliched as soap operas are, they're also very complex. Most soap operas (especially ones that last for years) are written by the writers as they go along. So even they don't know how the plot is going to end up. We are glued to our seats because we don't know what's going to happen next. The surprise element is very important for a soap opera to do well. Otherwise, the viewer will quickly get bored.
I also think that most of us can find characters in soap operas that we can relate to and connect to. In every soap opera I watch, I tend to like and support certain characters over others. If they are happy, I feel good and if something bad happens to them, I'm upset.