If most people moved on when there were problems in the R, look how many self-centered people their would be. There would be very few people Dbing.
Ok fewer STDs, kids growing up with one set of parents, people willing to form/build extended family networks, financial security for the short and long term/generational, all forms of stability.
I think if the government took and owned all the housing and rented it out to people, community pride would drastically decrease. You would see more crime and blight.
LTR build a sense of ownership, commitment to the LT success of groups of people and individuals.
Sure, some LTR's just suck the life out of people. That is a problem with the individual, not the pair bonding model.
Cac4 inheritance/property Along those lines, are the people that marry with in a select group, to keep the property/money better off and more stable than in societies that find random partners. I am not concerned about genetics, just social strengths.