>like in the western world mary Jeff Bezos divorce him next day and get half of his money
Instead of only one day it took her nearly 26 years (1993-2019), but MacKenzie Scott (former Bezos) did exactly this. And she got only 25%, which seems a little too less to me in regard of her help in building the company. According to Forbes shes at this moment number four of the world's most wealthiest women.

>the reason is to get a marriage at all.
>And what is your reason to believe so?
Its the part on pages 262 to 264 of Gerry Mackie's text (source citation see >>1681).
TL;DR:
>People prefer to support closely related children rather than unrelated children. Women seldom question the relation, but men never can be 100& sure. OTOH women often doubt a man's promise to support her and the children. Both want assurance. Hence, marriage is prefered to nonmarriage, because it "is intended to exchange and to enforce these assurances."

>Stratification diagrams of inegalitarian societies would be represented by a pyramid. It would show a few rich starting at the top going down to a mass of poor at the bottom. The rich men can each support a lot of women and their children, so they are more attractive to women. Unfortunately each woman gets less time with the man, the more women he has. Therefore they might "seek insemination from men more available than he". In return the man will "inflict costly methods of fidelity control: enclosure, guarding by eunuchs, hobbling, the honor and modesty code, and so on." In order to get to the pyramid's top the people on lower stratums will "imitate and exaggerate fidelity-control practices so as to gain economic, social, and reproductive access to the" higher stratums. Women are marrying up, conjugal practices flow down.

>"However the custom originated, as soon as women believed that men would not marry an unmutilated woman, and men believed that an unmutilated woman would not be a faithful partner in marriage, the convention was locked in place. A woman would not choose nonmarriage and not to have her own children; a man would not choose an unfaithful partner and not to have his own children."

IMHO, climbing the social ladder is the effect and the seeking for guarantees is the cause - not vice versa. As long as it takes to saturate all stratum levels it might even be the primary urge, but later it is no more than a pleasant concomitant.

>So why not get the best out of both "worlds"?
>Because [...] there is no such thing as "equality" everyone gets different set of privileges and obligations
Yes, some are "more equal" and your description includes many truths. But those ideas are not about reality. They just grant options. TBH, I did't mean it that serious. ;D