Quoting Lil Michael's Mommy:" I got into a discussion about my relationship with my grandma the other day. She asked now that my SO ... [snip!] ... to love someone" and he is afraid of divorce cause the only couple he has known not to get a divorce is his grandparents."
I think it's a personal choice.
To me, being married before we tried for kids was important. We got married because it was something we wanted to do. Not everyone feels that way,.
Do people look down on not being married? Sure, but it's a lot more common now so it's less of an issue, but a lot of people do still look down on it.
There are a lot of legal reasons to marry as well, such as having a lot of rights you wouldn't otherwise have. I don't believe it ruins relationships, those that divorce I think would have separated even if they hadn't been married.