Scientists agree that humans are neither a pure pair bond strategy species (Monogamy) nor are we purely a casual mating strategy species (polygyny), where a few top males successfully compete for sexual access of the females, then invest little or nothing into the offspring. Humans have both strategies pre-programmed in their brains and we exist on a continuum between these two strategies. Where any specific individual falls on this continuum depends on a number of factors (which needs more research but is most likely some combination of genetic personality, life experience and culture).
Parental investment theory states that because women invest more in children they will be more selective with whom they mate and men will be more interested in sexual variety and will compete for access to mate with females. Therefore it makes sense that monogamy, marriage and pair bond strategy has developed as the primary strategy across cultures due to this female preference and because it decreases the odds of male paternity uncertainty, but there could be more to this story.
Men have a bias towards mates with signs of fertility (young and beautiful). Women share this bias towards attractiveness (good genes) for short term mating, but more importantly they have a strong preference for mates whom are willing and able to stick around and provision offspring (pair bond mating). Typically this is high status older men with resources who are more established within a culture or community. This means that in terms of social capital, rich (often older) men and (young) beautiful women have a huge advantage.
The really interesting dynamic is that if a culture did not have marriage or pair bonding as its base strategy, then there would be a tendency for most eligible women to climb the social latter by only hooking up with high status men with the most resources, social standing and power (normally older men). This would leave very few and less desirable women available for younger men in the lower class to compete for. Evidence supports that low resource holding young men are likely to engage in high risk behavior (i.e. crime) in order to gain the resources to attract desirable mates. This could have very detrimental effects on society as a whole. It is possible that there is a tendency for any culture that did not have marriage, monogamy and pair bonding as the basis of their cultural system to have been out competed by cultures that encouraged monogamy. This is because monogamous cultures gives more opportunity for younger low resource men to find desirable mates who will then be less risk taking and make their efforts towards being productive members of society and supporting their families.
There are some some exceptions to this rule, but this theory would predict that these cultures would have a stabilizing mechanism, to prevent young low status males from causing problems in society. The most obvious example of this is the Mormon Culture.
Historically (not current day) church leaders (high status older males) would have multiple wives typically adding young women to the family as they come into sexual maturity. To prevent the young men from causing problems in the society, they are sent away on a "Mission" to convert people to Mormonism and this also gives a strong incentive to convert a young woman to become the young mans (1st) wife, as there would be very few eligible mates back home.
This model would also predict that polygamous tribes could channel the high risk behavior of low status males into warring with neighboring tribes for resources. Research show that in tribal warfare the kidnapping of women as part of the spoils of war raids is found across many traditional tribal cultures (New Guinea, South American and African tribes).
Both these exceptions are only evolutionary stable strategies in relatively smaller groups (as compared to nation states). For the Mormons this is only sustainable as a sub-culture, because if it was the dominant culture there would be too few women for lower status males. As for the polygamous tribes it would only be sustainable at a size where there are other small tribes near by in which to steal women from.
The other exception to this tendency that comes to mind is that there are polygamous cultures that are stable, but it is rare within the society and only the most wealthy and high status males have multiple wives, so perhaps there is some threshold where if only the very elite have multiple wives it does not create enough of a shortage of eligible mates to have any noticeable detrimental effects.
Furthermore, this is in no way speaking out against polyamory (non-exclusive mating) as a sub-culture, but it does shed some light on why it is, has been and will most likely remain a sub-culture and not the dominant culture for any large civilization or nation state.
Further readings
1) Cavemen With Smartphones: how evolution shaped history and finance
by Richard Amador (in section 3 part 8)
Cavemen with Smartphones: how evolution shaped history and finance https://www.amazon.com/dp/1916008801/ref=cm_sw_r_cp_apa_i_mebqCb2DFNNRP
2) The World Until Yesterday: what we can learn from traditional societies
By Jared Dimond