Yesteryear's marriages were also boring for some, it's not a new phenomenon. Yes, there is probably some effect in terms of psychological support from an extended family, but I doubt that that would have been more powerful (demographically) at discouraging divorce than the social stigma. Plenty of times that extended family was telling the individual to stay with the abusive spouse or else the family would be shamed. That's not a social environment to be proud of - who gives a fuck about the family name if the members have to live in misery to maintain it?