>>82260565
Because nature is retarded.
But the effect you are describing is only applicable in the future world of full freedom and liberation, it wasn't what it was optimizing for in the past.
>Until 50k years ago:
There were 2 culture variations.
1. Everyone did it with everyone else but because of timing and semen quality, quantity & frequency, some passed on more. Or
2. Women were traded goods. The highest status male with strongest political coalition members that wouldn't kill him got to take upto 3 of the best wives(not too many to keep the rest happy), best as in most attractive and youngest to make most kids over lifetime and lower mortality rate of kid, she'll be traded down later to switch to better women. Top status males get the women, the rest don't. Competitions were necessary to gain status, gain coalition and get access to women. This is why most modern men are subhumans internally, around 45% of males(40% white, 50% black) in US gets arrested at least once by age 23 for non-traffic related reasons, so the actual chimp out rate is much higher that doesn't go to arrest.
>Around 50k years ago:
To reduce cost of male male competition of everyone killing each other for access to women, tribes with cultures that killed each other less flourished more. This was achieved by the invention of marriage. Everyone goes without women until of age, after they are handed a woman and then they keep them for life. Some may get more than one or switch around but it's largely 1:1 with male female ratio. Males focused more on their offspring instead of competing for more women as it was against cultural sanction. Tribes thrived and culture spread.
>Around 10k years ago
Culture of marriage remained but power was centralization as people don't move around with food anymore. They need central organization to survive and can be controlled. The ones at top and their friends marry as much as possible and rest gets used as slaves and with little to no chance of marriage.
