Open Question: Why is it so rare to see a Black nuclear family anywhere in public?

It's common to see Black men with women of all other races and the mixed children, but it's almost unheard of to see the Black males with Black females in public. No other race is comparable to this particular amazing social phenomena. I was born in SF, and raised right outside the city when it was home to about 120,000 African-Americans... and I never saw it! Not nuclear families I didn't.