Marriage is between people, but it's also between the people on the one hand and the community on the other -- it's not just "Chris loves Pat" it's "we all recognise that Chris and Pat are a family now, yay!" It used to be perfectly reasonable that this was marked with a religious ceremony at the church door in communities that all shared a religion and place of worship. These days this makes less sense.

Yes, that's really true. It's awfully unclear these days exactly what's being invoked when we say vows-- God? Our families (esp. our mothers-in-law)? The community we work with? The community we play with? The neighborhood? The law? When all these things were more or less the same and united, the question didn't come up-- and now that it has, we don't know what to do with it, in part because we're trying to maintain the illusion that "marriage" is something which has been exactly the same lo these many generations.