Most Helpful Guy
Possibly a feeling of commitment or loyalty or honor. Also, a big thing to consider is some people put huge investments into relationships. Time, money, having offspring, debts that are easier to pay off together (mortgage or life-savings). As well, coupled with the later, you may have your investments combined and that it takes a lot of legal bullshit and money to separate your names from. So relationships can get very complicated and it's easier on paper to just say, "Let's get a divorce.", or "Let's end it." than it is to actually do so.