Things are not so black and white in life,there's finances, family, and even happiness or contentment in some ways ,a sense of moral obligation etc that makes people stay in situations that are not ideal but I don't think it is as bad as it first sounds,it really depends on each case and how great the issues in the relationship are , I guess as long as there's respect and friendship one can find happiness outside of romance.
@PepsiColaP That's very true but it takes a lot of effort. As you get older you wonder if you should have put the effort into achieving something better more fulfilling