In "Living in Sin," the contrast between what the woman thought her relationship would be like, and what it is actually like, shows some serious, mega-value-sized dissatisfaction. But even though she does more than her partner to "clean things up," she really doesn't put a whole lot of effort into making the situation better. This lack of effort makes us wonder whether, in the end, she's not just dissatisfied with the way things turned out. Maybe she's also dissatisfied with her choice in partners.
Dissatisfaction should cause people to take action. Nobody should stay unhappy, and the couple in the poem should either work harder on their relationship or let it go. Fish, or cut bait!
They've got nobody to blame but themselves. People who stay in unsatisfying situations are usually bored and apathetic, so they are not stimulated or inspired to do anything about it. This is probably what caused the relationship to deteriorate so much, and it also explains why the couple isn't doing anything about it.