I highly censor myself on HN as I know most of my views are in the minority, but I'm happy to see your response.
To add to your point, I've also found that developing the relational skills necessary to bring a marriage relationship through tricky waters often leads to success in similar, but perhaps not so dire, circumstances.
It's also been common knowledge for some time now that children tend to do much better when stability is present in the home. If a child always thinks one of their parents might just up and leave one day, they tend to act accordingly (read: exhibit undesired behaviors).
I understand marriage isn't for everyone, and I certainly don't promote it as such, but I also wouldn't advise people to treat marriage as no more than something that can start today and end tomorrow, on a whim.