Why is marriage mainly a secular matter in many Buddhist traditions?

In many Buddhist traditions, marriage is considered primarily a secular affair because the core focus of the religion—across the Theravada, Mahayana, and Vajrayana schools—is the attainment of enlightenment.1

Unlike traditions where marriage is viewed as a divinely instituted sacrament or a religious duty, Buddhist literature generally treats marriage as a personal choice between the two individuals involved. While the Buddha provided guidelines regarding the responsibilities of lay householders, these teachings do not elevate the marital union to a religious rite in the same manner as other faiths. Consequently, because the religious framework emphasizes individual spiritual liberation, the regulation and performance of marriage are largely left to secular custom rather than religious law.21