Childless people who stay in loveless marriages are at least not hurting anybody but themselves, so if they choose to be miserable, that’s their right. People with children who stay in loveless marriages, however, destroy their children’s chance at having happy, fulfilled personal lives when they grow up. The children grow up, observing as their basic model of romantic relationships a boring, miserable marriage. Of course, they will end up perpetuating the model because that is all they know. It is profoundly wrong and immoral to inflict this damage on children for the sake of convenience.