I find it really helpful to try and think about what the legal elements of the law are trying to describe, Because marriage has specific legal forms, and social forms, but they kind of revolve around what is a kind of emergent biological/social phenomena.
It's really about a couple, who will usually eventually have offspring (at least historically and usually even now) going from being two separate economic units, to being one single economic unit.
They will still each engage in what is broadly economic activity, be that agriculture, hunting, caring for kids, maintaining the home, or working at a factory. But the efforts and benefits and sacrifices are managed as a whole, balancing the best overall outcome for all. It's kind of a natural for of everyone giving according to their abilities and what's best for the group, and each taking according to their need, again within the context of the overall health of the group.
Much like a communal tribal economy, there is no good way to untangle who owns what. They are an economic entity with parts rather than a group of 30 independent economic entities.
Marriage laws and customs are usually intended to keep intact the integrity of that entity and make sure it works for the long term health of society, and also protects the interests of the individuals. (Which some places do better than others!)
So any individual entering that kind of agreement finds they both gain and lose, and that it comes with obligations as well as benefits.