Gnome, that was the problem I kept bumping up against when researching: how can you try to make the infinite, kaleidoscopic variety of family arrangements fit another set of rules, any better than they do the existing? It's never simple, is it. But then, to an extent all private family law consists of trying to force messy, nebulous, non-linear human relationships into some sort of predetermined mould, so you can work out what the hell to do when it's all gone to hell in a handcart. I seem vaguely to recall autopoeitic(sp?) theory holding that law is an inherently inappropriate means to try to regulate families and their mutual obligations, for just that reason. Whatever you do you're going to be imposing an injustice on someone, at some point. Multiple someones in fact. The only question is how far you can reduce that, and if you can try to make it least likely to be the most vulnerable.
olgaga, I think the expectations are to do with expectations of social roles, in many cases, rather than financial responsibilities. That's actually a factor in most marriages. When we were first married - no kids, both working - even my own DH started huffing about stuff such as sausages past their sellby, or baths clean enough. I just said if he wanted to be a sexist twat he could look online for divorce papers; if he wanted to be reasonable, he could explain why precisely he was incapable of reading a sellby date himself, or cleaning a bathtub he also used. He stopped, apologised, and agreed he was in some way responding to his own internalised conception of marriage. He's (mostly) managed to avoid that crap since. But I deal with those conceptions from my in laws quite a lot (and used to from my father, too). I'm not too bothered, because DH is also a thoughtful person who understands my irritation. And we live a long way from my in-laws, so we see them rarely. But a lot of people don't have that situation, or just aren't willing or happy to set that social and emotional weighting aside, and why should they? That social weight of expectation is totally separate from wanting financial protection and recognition of a non-monetary contribution to family life.
"Aside from the obvious obligation of a parent to a child, you can't force obligations on to people who refuse to accept them. The whole point of marriage is that you mutually agree to obligations which confer lawful rights on each other."
Well, no, actually you can. That's how de facto law works, and a lot of jurisdictions have it. It's conduct based, rather than formal agreement based. There are arguments against it, good and valid ones, clarity of intention not least, but there are also excellent arguments for it. There's no right answer. Costs and benefits go with each.
EdgarAllenPimms, in this thread, again and again people seem to be saying that if others don't want to share their life choices, no other options should be available because that alone makes the differing position illogical. That they just need to stop feeling the way they do and see it all logically. But it isn't about logic; families, life partners, and the emotions we feel for them. Very few people decide to marry because they want legal protection if their spouse beats them, or leaves them for someone else after 30 years, or they themselves fall out of love and want to leave. People marry because they're in love and want to build a family together, usually. It's emotions-based, not logic. So why, then, demand that others are logical in accepting marriage now that it can be stripped of most wording that would support its being oppressive, if the mere idea of being "legally wedded" and a husband/wife makes them squirm? And if a lot of people sincerely want a new model, without the heavy weighting of historical resonance, then why block that? For what reason?
Finally, as rhetoricians has pointed out, Ireland has a system similar to the one I ended up thinking we should have after researching (clever Ireland ;)), and allows CP to gay and straight people on equal terms, and the sky hasn't fallen in.
In brief: the current system works for a lot of us. Lucky us. But if it's not working for a lot of other people, why can't it be altered, or expanded to encompass their needs, too? Why insist people should fit our model, when another exists they would prefer?