Why is marriage a life benefit?

1. A key contributor to African American socioeconomic disadvantage and
welfare dependence that spanned generations. Solo parents (typically
mothers) who lack a partner to cooperate and consult with about
parenting decisions and stressors tend to exert less control and spend
less time with their children, although those associations are confounded
with socioeconomic disadvantage.
Father involvement is particularly beneficial for resident children,
although nonresident fathering remains associated with well-being.
Therefore, the conciseness is that nonresident fathers are less involved
with children, on average, especially if their parenting responsibilities are
spread across multiple households.
Indeed, child poverty is highly differentiated by family structure, ranging
from a low of about 7% for children in two-biological-parent married
families to a high of nearly 44% in single-mother families.
AnnBrown.S, Marriage and Child Well-Being: Research and Policy Perspectives, J Marriage Fam. 2010 Oct 1; 72(5): 1059–1077

2. The signal role of marriage is in alleviating poverty,
thus minimizing societalills. Fostering child well-being
is at the core of ongoing community effort to
encourage “healthy” marriages and responsible
parenthood.
As the rate of marriage declines nationally, primarily
with millennials. The current marriage debate centers
on questions concerning the role of government in
encouraging marriage and discouraging unmarried
childbearing. These policies are primarily directed
toward at-risk groups, namely the low-income and
poor populations who rely on government assistance.
Brown.S, Marriage and Child Well-Being: Research and Policy Perspectives, J Marriage Fam. 2010 Oct 1; 72(5): 1059–1077