The fact is traditional religious marriages prior to the modern age were only done to insure the wealth would be passed on to the male side of the family should the patriarch die. Even so, in some cultures such as Middle Eastern ones and Africa, the wife was not even allowed to inherit the wealth and possessions, and she would be forced to remarry a brother, uncle or cousin of her husband just to maintain her possesions and financial security, unless she had an adult son, in which case it would go to him. Which would force mom to be at the mercy of her son for support, and if she remarried someone else, she would have nothing.
Meanwhile, the traditional religious marriages we have today, are not really that traditional at all, from a historical perspective, even in this country. They are primarily contractual financial arrangements that offer over 1000 benefits to a married couple, that an unmarried couple does not have access to, and whether they have kids, or not. Which is a prime motivator to get married, isn't it? Of course it is. Without all those extra benefits, there would be a lot fewer marriages, you can count on it. And even saying marriage is done to preserve the family unit (kids) is now a bogus argument with divorce rates well above 50% in many countries around the world.
Now when we talk about India and same sex marriages hundreds of years ago, the reason they didn't do it is because they didn't have too. Try to wrap your head around this fact. Can you figure out why they didn't have to get same sex married? Because usually they would live together with one of their families and help with chores, farming or whatever, just like everyone else in the family did. And keep in mind we are talking LARGE extended families living together and sharing everything - except whom they slept with at night. If one of the same sex partners were to die, the family unit would continue, or the partner who was left might go back to their family.
And another thing, using India as an example, it was far more common for men to be gay than a women, because a woman's status was considerably less than a males in the first place. Women were largely bartered then for marriage just like they still are in the Middle East and Africa, so a woman simply had far less opportunity to even express a gay desire for a relationship than a man would because she was a man's PROPERTY.
I hope you learned a little bit from all this, but I sincerely doubt it. And if anyone from India would like to chime in and add anything or correct my perspective, please feel free, because this might be factually in error a bit because I read about this a long time ago, and I'm fixing to log out to get some rest ATM.