is it? marriage in the US for example is what we would call "official marriage on paper". people just as easily like together or not but remain boyfriend/girlfriend for years, even having kids because why not.
For these people, getting married is officiating something that doesnt need it or going through legal hoops.
in other countries, getting married is basically the only way you can "officially" or socially acceptable manner of being even in contact with the other person, not to talk about "having kids before marriage". "bastard" is still being used in india to refer to a child not born out of wedlock as a type of slader and here you talk about "what matters more".