People assume it because most women do change their name upon marriage.
It's therefore reasonable for them to assume this as the default position while accepting that the women may correct them.
It's no big deal, is it? Just correct people when they do it. Don't see what the fuss is about.
Nobody has to change their name, anyway; there's absolutely no reason to do so. It's personal preference.
I really don't understand changing name to partner's if unmarried, though. If you like traditional marriage-y stuff, get married.
Also, legally it means nothing. People aren't somehow legally married because they call themselves their dp's surname. I'm not suggesting that the people who have said they've done that here think that it does so please don't think that I am. Not at all-but there are people out there who are so dumb that they think that it does.
Just like a woman who is married who keeps her maiden is as married as one who takes her dh's.
I can understand feminism not liking marriage because of it being a patriarchal institution and robbing of women's individuality, but all this fuss over something that:
women don't HAVE to do as regards marriage itself e.g. being given away, taking dh's surname, I really do not get.
As for being an argument for registered partnerships, if these partnerships are legally same as marriage, why have two systems i.e. marriage and registered partnerships because people have problems with things they don't have to do like changing their name? 