Why marriage? How does marital status varies from ‘staying together’-status?

save money on taxes for one thing lol. it's harder for either partner to just up and leave for another so there is a higher degree of commitment. if you are married you have to get a divorce if you want to just up and leave. if you are just living together you can up and leave and never talk to each other again.

also if there is some sort of medical issue if you are not legally married the immediate family has more legal power over things like ending life support, or power of attorney in the case of a will or death.

if you are just living together you really don't' have many legal rights in terms of a spouse.

though in some places common-law marriages are formed if you live together long enough it depends where you live though.

but in general legaly speaking wife trumps girlfriend/boyfriend and family trumps girlfriend boyfriend if the person is unable to speak for themselves.

Marriage as ceremonial bond, appeared as a necessity in population growing societies. To the core of its meaning, it prevented bloodshed by clearly stating patriarchal ownership guaranteed by society.

"Staying together" is the sociological basis of that, but without collective identity determined by the evolved stage of society.

Legal status

Being married you have rights.