Just from a resource and time management efficiency standpoint, the
married, wife-mother/husband-father family structure consistently provides
better direct and community outcomes for children than the single-mother/single-grandmother
headed family structure that is disproportionate in our community.
Married couple w/children: expenses to support one home; coordinated schedules; sharing of household duties; both parents available to directly nurture studies in the evening and morning; children have in-house male and female gender balance; cooperative relationship modeling in-house; two sets of biologically-related extended family members available for child care
Unmarried couple w/children (including out of wedlock and divorce): usually need expenses to support two (or more) separate residences; uncoordinated schedules; separate household duties; only one parent on-site to nurture studies in the evening and morning (if not at work); children have single gender presence; single-parent rule in-house; legal fees and arrangements needed for custody, support, visitation matters; usually single mother's extended family available for child care
Its just that simple.