I mean, people usually consider stability to be a good thing, especially when there are children involved.
Beyond that, legal marriage has benefits that (for lack of a better word) "pretend marriage" doesn't. Some examples include potentially lower taxes, employer benefits for spouses (such as insurance), spousal social security, spousal pension benefits (widows/widowers are often allowed to collect their spouse's pension for the rest of their life), no gift tax between spouses, Spousal IRAs, military benefits, automatic tax free inheritance, next of kin status (which matters if the spouse is incapacitated), lower insurance rates, spousal immunity in court, eligibility for FMLA to care for a sick spouse, eligibility for bereavement leave if a spouse dies, eligible to sponsor a spouse for immigration, etc.
Married couples have the "benefit" of going through divorce if they break up. Divorce proceedings allow a (hopefully) neutral third party to order legal division of marital assets. I've seen some incredibly messy non-marriage breakups, where going through divorce once would have been less messy.
There might simply also be a social component of marriage that cohabitation simply doesn't provide. If you are married you may work to stay together rather than just split up when you hit a roadblock. Whereas if you're just dating then you might just break up at the first roadblock rather than try to work things out. No data or anything, that's just my "gut feeling" on the matter, it just "seems" like that's the case. Of course it could just be the people who break up rather than work on issues are just not getting married.
Beyond that, legal marriage has benefits that (for lack of a better word) "pretend marriage" doesn't. Some examples include potentially lower taxes, employer benefits for spouses (such as insurance), spousal social security, spousal pension benefits (widows/widowers are often allowed to collect their spouse's pension for the rest of their life), no gift tax between spouses, Spousal IRAs, military benefits, automatic tax free inheritance, next of kin status (which matters if the spouse is incapacitated), lower insurance rates, spousal immunity in court, eligibility for FMLA to care for a sick spouse, eligibility for bereavement leave if a spouse dies, eligible to sponsor a spouse for immigration, etc.
Married couples have the "benefit" of going through divorce if they break up. Divorce proceedings allow a (hopefully) neutral third party to order legal division of marital assets. I've seen some incredibly messy non-marriage breakups, where going through divorce once would have been less messy.
There might simply also be a social component of marriage that cohabitation simply doesn't provide. If you are married you may work to stay together rather than just split up when you hit a roadblock. Whereas if you're just dating then you might just break up at the first roadblock rather than try to work things out. No data or anything, that's just my "gut feeling" on the matter, it just "seems" like that's the case. Of course it could just be the people who break up rather than work on issues are just not getting married.