I've heard that arranged marriages end up as loving relationships. If choosen as compatible and with no choice but to make it work... plausible. Or it could be that people put up with damaging situations.
* compatibility is established by design
* usually, its a union of families, which creates a wider social circle that helps out the newlywed couple through difficulties
Personally, I believe that _any_ two people living together and sharing so much will inevitably end up loving/hating each other. You simply can't be indifferent to people who are in such close social contact with you for so long.
Also helping are having kids if only because it creates and orders the TODO list when a baby cries or a child needs food, shoes, etc.
Also helping are well established ROLES. Both husband and wife already know in good terms what they are to do.
Also helped was the village church and the weekly services emphasizing family formation.
Also helped was village social pressure, at times really severe.
Or put another way, you can find a standard by which the marriage worked out. But is it a relationship that the people involved would want to freely choose?
Part of the problem as I see it is that folks in the west often use their freedom to select for stupid things. (Omg she likes the same music!) My cousin just got matched up with someone where the criteria was: “she’s an engineer, her family is respectable and she’s not too religious.” I suspect it will be a good match.
That era also have a lot of jokes about marriages that ends up with both partners despising each other and calling each other names.
Couldn't we simply have tax breaks per children and be done with it?
In other cultures, the most common other arrangement is to give the child's mother's brother (uncle) all the rights and responsibilities that we give to the biological father/husband. The uncle rears the child, with the mother. Marriage can exist in those societies but gives no rights over the child, and no or few responsibilities. (Might be time to consider offering this as an option for people in this society, at least.)
Children are little consoled by tax breaks, in my experience. Single mothers can't stay home on a tax break, since there's no income to get that break from.
Seems super unlikely to be the "most common" (by number of societies) arrangement when it only can work like 50% of the time in a society that DOES decide to do it. Was your Anthropology professor pulling your leg?
Stable population size in any significant society is a very new thing, not historically common. Basing your assessment of historical likelihood on societies being assumed to have a trait that basically no premodern society did probably isn't reasonable.