The church used to provide that structure, combined with private contracts (prenup, insurance, property titles, last wills, etc.) that you could use as evidence in ecclesiastical courts.
Then the state took it over and came up with a sort of "package deal" called "marriage and family law", but it's kind of a mess, so people are leaning more toward private contracts again.
"Trust me, girl, I pinky swear", is a private contract, but like 🥴