Two people can care for one another without marrying. Marriage adds a recognized social and, often, legal relationship: others can understand that certain commitments exist without negotiating their meaning from scratch each time.
Those commitments may concern care, property, children, inheritance, kinship, or religious obligation. Marriage has been understood both as an institution and as a relationship shaped by the participants’ choices. Different understandings give different answers about which obligations are fixed and which can be revised.
Public recognition can make cooperation easier by clarifying expectations and giving a relationship standing with institutions and families. It can also bring expectations the participants did not choose, especially where gender, family authority, or social status determines whose preferences count.
The ability to enter a marriage is only part of its design. The ability to refuse, negotiate, own resources independently, or leave matters too. An arrangement can promise protection while making dependence difficult to escape.
The same name can therefore cover different commitments and distributions of power. What matters to the people involved is which obligations others recognize, what each partner can decide, and what happens when care or cooperation breaks down.