Traditional marriage was designed to ensure the labour contribution towards society by beta males. In return the beta male would get exclusive reproductive rights towards one woman. This enforced monogamy gave all men a non violent way to compete for mating opportunity by labour. But after women's sexual (liberation), the introduction of no-fault divorce and other law changes. This is no longer a viable mating strategy for men. As marriage only locks down a man financially. But modern marriage does nothing to lock down a woman sexually. The woman is entitled to the man's resources rather she stays with him or not. But the man doesn't have any sexual claim to her anymore. So what's the benefit for men? There is non! We are back to the stone age sexually. The most dominant alpha males get most of the sex with young and attractive women. And the majority beta males have to keep competing for the leftovers. Marriage only benefits women. And most young men have no reason to contribute towards society anymore.