That whole separate but equal thing works both ways:
A heterosexual Austrian couple have embarked on a court battle to have their relationship legally recognised as a "registered partnership" - a new form of civil union for same-sex couples....Meanwhile, the kind of pared-down marriage they want is proving a huge hit with straight couples in France, where 95% of couples taking up the pacte civil de solidarite (Pacs) in 2009 were heterosexual. As the number of straight French couples opting for Pacs has grown, the number of marriages has shrunk, to the point that there are now two couples entering into a Pacs for every three getting married.
Apparently many straights feel partnerships are "a low-risk stepping stone to marriage." A quote from a heterosexual Pacsed woman:
"To me, it doesn't replace marriage. I'd still like to get married one day."
(Hat tip: Kincaid)