The author has a myopic view of actual trends in American society. If the nuclear family was such a successful idea, why has unwed motherhood been rising stead

The author has a myopic view of actual trends in American society. If the nuclear family was such a successful idea, why has unwed motherhood been rising steadily since the 1940s, with two big peaks in the 90s and 2010s? Has the nuclear family had an impact on parts of American society that depend on close connections to extended family, such as Chinese, Indian, Latin, etc? Young people are actually waiting longer to get married now, and much fewer people are getting married when they get pregnant while unwed.