[gyardley]

You know how sometimes when you're looking at an old codebase, where all the developers who've written it have moved on to other jobs, you see a little bit of code that doesn't seem to make sense? And then you remove that code, and then and only then do you find out exactly why it was there in the first place - usually in a rather painful way?

Well, things like marriage are the societal equivalent of that bit of old code. We're 'stuck' with it because (for the vast majority of people, anyway) it serves a useful purpose, one that only becomes apparent when you go without it. That's not to say we can't and shouldn't change the institution - it not like it hasn't been evolving over the centuries - but it'd be wiser to make changes cautiously, experimentally, and locally rather than just 'moving on' as a society.