Some bad answers (and non-answers) to your question here. There are many studies on this with various conclusions worth reading, example set [1]. At a high leve

Some bad answers (and non-answers) to your question here. There are many studies on this with various conclusions worth reading, example set [1]. At a high level, US marriages (and potentially non-US long-term partnerships) bring stability, additional economic support, an additional role model (completely missing for boys growing up in a single mother household), additional attention & emotional support at home, and the ability to split parenting tasks as the need arises (ex. dad goes to a school event because mom needs to work late, or vice versa). Also important to note is that parental attention has a large impact on academic outcomes of kids [2], so in single parent households where the parent doesn't have the time to provide sufficient attention, the kids suffer at school compared to their two-parent peers. [1] https://scholar.google.com/scholar?hl=en&as_sdt=0%2C44&q=two+parent+households+child+development https://scholar.google.com/scholar?hl=en&as_sdt=0%2C44&q=two... [2] https://www.tandfonline.com/doi/abs/10.1080/00131911.2013.780009 https://www.tandfonline.com/doi/abs/10.1080/00131911.2013.78...