Even single people should be thinking through high risk decisions, so I don't really see your point there. A dual income couple has inherently more ability to make higher-risk decisions that have larger expected returns.
As for time spent working, I'm a bit skeptical of that. It's not like single people don't have socialization needs that need to be met. My single friends spend a lot of time and effort on dating and trying to arrange opportunities to see friends.
I think the point is that the decisions aren't as high-risk when you are single and don't have other people to support (especially children). The consequences of failure aren't as high.
Instead of being able to share a place with a few people (maybe even sharing a room) and sharing utilities, internet, cable and so on, you are paying significantly more for housing, food, utilities, transportation (bigger car), clothes and insurance/medical costs. Those costs could easily be 3-4 times as much as a single person.
If you are a dual income family, you may also be paying for child care and have the extra responsibilities of getting your children to and from child care and/or school (let alone actually spending some quality time with them). Working late has a much higher cost and being out of a job has much greater consequences.
My point is that these days, especially accounting for assortive mating, a married person is better seen as having someone to support him or her, not as needing to support someone else.
Your roommate isn't going to pay for your food and rent. Your spouse will. Moreover, old married people are much more likely to have assets to draw on if someone is unemployed than single people. And while they may have higher expenses, a lot of those (like child care) disappear when one person is unemployed.
Just looking at my friends, very few of my single friends could tolerate loosing their jobs as well as my married friends. That includes older couples I know with kids.
As for time spent working, I'm a bit skeptical of that. It's not like single people don't have socialization needs that need to be met. My single friends spend a lot of time and effort on dating and trying to arrange opportunities to see friends.