Historically, marriage has been a tool, an economic transaction that arose because of certain material conditions. However, this kind of forced, strict monogamy is not natural to humans and can in fact lead to unfortunate situations. Domestic abuse for example is, I think in many cases, caused by the general tension created by forced monogamy and forced cohabitation of two people that often don't want to be together anymore.

The amount of force that has historically been used to save marriage as an institution is ridiculous and includes:

1)Brainwashing

2)Legal repercussions (for example "bachelor tax")

3)Suppression of sexuality to the point where certain culture even mutilate female genitals.

4)Severe societal pressure.

5)Manipulation and lies.

Even today we see that divorce rates have sky-rocketed and many marriages are generally miserable. It's clear to me that this legally binding forced monogamy is a failure and anti-human nature.

Of course the main reasons why people are trying to save marriage are economic at their core, as the nuclear family itself was created because of certain material conditions. The thing is that I believe these economic reasons themselves should be questioned and challenged instead of trying to save such an oppressive, anti-human and failed institution.