My partner has no interest in marriage (though she tells me I'm the first person she considered marrying if she changed her mind about it), and that's fine by me. Helps us maintain our independence. We are fervently against having kids at any point, too.
However, if I end up getting a fellowship to study in Italy or Greece for a year while I'm in grad school, the only way to get her to be there with me would be if we were legally wed, so the program I'm in would support her. But that would be a tail wagging the dog.