For many blacks, avoiding proper grammar seems to be an act of insolence and defiance, of “sticking it to the man.” I’ve noticed that recent black immigrants don’t usually have that attitude, and often speak excellent English.
You get that when black people deliberately mispronounce your name. It’s a “you ain’t the boss of me “ push. Fired my parents cleaning lady after one warning.
I worked with grad students from Africa who spoke beautiful English and I don’t mean just the English accent.
They spoke very well and made themselves understood...it went hand in hand with their lovely manners and unfailing courtesy.