Their own, local or ethnic one, and the one common, "proper" English.
Most of we 8th generation Vermonters have our own local dialects, different from one another and very different from "standard English".
However, most of us also became proficient at standard English to be able to communicate with others.
I enjoy hearing a southern Black accent and dialect, as well as many others, and I hope when I slip back into my Vermont twang, it entertains others as well.
You would think Blacks would be very offended by the low expectations of racist liberals.
I speak Jive
https://www.youtube.com/watch?v=RrZlWw8Di10