AA speak their own version of English - AA English - Ebony English. Put it in google. They grow up in area where parents, friends and also their teachers speak Ebony English. Even some books have been adjusted to Ebony English. And once you grow up its hard do change smth you used your whole live, especially thing like language.

Oh yeah...that one is the worse. The one I really hate is when people mispronounce the word Advertisement to Add vertisment or so it sounds. :error