I'm not interested in relationships at all, so i'll take your word on tax benefits as i haven't looked into that, but the legal benefits are real. it'd be in *everyone's* interest to move it away from marriage, but then you'd have to have people voluntarily updating paperwork for current boyfriend/ girlfriend and going through so many hoops that no one would keep it up.. which would mean that a parent could fuck over a kid's partner if they hated them. Which is super shitty, and happens with gay couples currently.