I touched on this earlier, and again Eiuol may have a better historical perspective to offer, but essentially marriage is intended to sanction the creation of families. The performance of the ceremony usually involves establishing the clear title of the man and woman getting married:
“We are gathered here today in the face of this company, to join together this man and this woman in matrimony; which is an honorable and solemn estate and therefore is not to be entered into unadvisedly or lightly, but reverently and soberly. Into this estate these two persons present come now to be joined. If any one can show just cause why they may not be lawfully joined together, let them speak now or forever hold their peace.” ~ Traditional ceremony
Being willing and available, the family names of the bride and groom are announced for the public record; both families releasing guardianship of their child so that a new family may be legally recognized. The bride and groom express their intent to share a long term ('til death do us part), monogamous (I offer you my solemn vow to be your faithful partner…) relationship with each other, as a socially autonomous unit (even the police are reluctant to get involved in marital squabbles). The presumption of course, is that the future husband and wife will produce and raise children, thus providing future members of their community, who in turn will provide future members to their community.
Politically, marriage combines individual rights into family rights (of husband and wife) to govern the raising of their children (as their property until they become adults). For the most part, traditional marriage is about the ownership and transfer of property (don’t cringe Eiuol, *snicker*). Of course these days it apparently “takes a village” to raise a child, so the politics are shifting from respect for family autonomy, to respect for the “beneficent” concerns of a community of interlopers. Children are still property, but they are in the process of becoming the property of the State… but that’s for another topic…
Pertaining to this topic, legal marriage is expressly for long term, monogamous relationships that create property in the form of children. Why? Because that’s what happens when men and women shack up, and frankly that (the creation of children) doesn’t happen when members of the same sex shack up. The language, e.g. bride, groom, husband, wife, father, mother, son, daughter, specifically highlight the necessary roles of gender within a marriage. So there’s no question of the context or concept of what a marriage is, and there’s no question that it isn’t legally structured to accommodate the biological offspring of same sex relationships. As to heteros who don’t marry, it’s a choice, not a legal necessity. mdegges, et al, may object to marriage and divorce entitlements, but those who choose to marry don’t, because obtaining legal security to have and raise children is a good thing.
So, if your objection to marriage entitlements is some form of Eiuol’s, “well, that’s not nice for nonhetero relationships, let’s not exclude them”, my response is, “cry me a river, build me a bridge and get over it”. All those “benefits” you covet can be obtained legally by other means, but no restructuring of marriage will ever address the legal needs of biological offspring of same sex couples; only adoption does that. This isn’t a civil rights issue, because not getting married certainly doesn’t prohibit the sexual pairing of consenting adults, nor does it prohibit them from adopting children. Marriage only reflects the biological reality of what happens (accidentally or intentionally) when boys and girls choose to spend the rest of their lives together.