You can bullshit all you want but the MAIN reason a lot of people get married is the financial and emotional stability it provides their lives. Not necessarily cuz they are madly in love and wanna be with a particular person the rest of their lives. On the conscious level they might provide a hundred logical reasons for marriage but deep down in the dark recesses of their minds many folks are motivated by fear. Loneliness, financial ruin, no safety net, going homeless, not being able to do "couples" stuff, especially with other couples. All these things are foremost on a womans mind when she gets close to 30, and a mans mind when he gets close to 40.
Rich folks foolishly believe they have fewer worries or are less likely to lose big if they make a huge mistake. Fear doesnt keep them in mind and they are really any more intelligent than their poorer counterparts, just knowledgeable about how to get money.