Why do you think so many that would have been slaves are now instead prison inmates, which means slaves to the state in which they are incarcerated. Many of them work at less than minimum wages on contracts between private enterprise and the various prison systems. It's not uncommon for prisoners to be doing phone work for private industry, who in turn pay the state, the new owners of these slaves, for the privilege.
Why do you think so the majority of black people still marry other black people, the majority of white marry white, and so forth? Probably for the same reason normal men have sex with women instead of other men. It's Nature. God created Nature.