I live in Mississippi and have seen it for 50 years. An unmarried mother of several children receives a windfall of welfare benefits, getting married would stop most of them. Hence the reason the illegitimate birth rate is approaching 90% in the black community. Having babies is a career here, it's a way to guarantee a stable income from your teens through middle age. It's lucrative also, by the time you add up all the benefits like free housing, child care, food stamps, medicaid, etc. they can haul in close to $100K a year. For a young girl in high school who probably can barely read the ink on her diploma having children pays a lot better than any job she'd be qualified for, sitting home having kids & smoking pot pays a lot better than getting up at 4 am for the breakfast shift at McDonald's.
Frankly I don't blame them, it's a failure of our enormous welfare state that welfare pays so much more than work so they're incentivized to go and stay on welfare. Someone mentioned that they get cut off if they cohabitate, that's true but easily worked around. They don't admit to cohabitating and no one checks, they change partners frequently anyway so the guy isn't likely to be there long term.