Almost everyone does it, it’s not a race thing. With the internet and TV these days it’s more an economic thing but it’s still a bit of a regional thing. And regional can mean the difference between neighborhoods in the big cities or the North-East vs. South-East mountains (hillbilly country.) There are plenty of white folks raised in the projects that have to learn the same thing. And there are people like me (white, lower class, but from a fairly homogeneous small town) who learn to switch in the other direction to fit in with co-workers. You know there is a big difference between northern “black speak” and southern? Put a thick accent on top of a thick accent and it becomes very hard to understand, I can parse Northern just fine but it took me several weeks to get comfortable just because I couldn’t understand what my coworkers were saying working fast food in Memphis as a Yankee. They would “switch” for me when I asked them to repeat themselves at first, it helped me learn the vernacular. I appreciated it, and it wasn’t because I was white, it was because I’m a Yankee. After a while they didn’t need to so they didn’t, and I didn’t need to “switch” for them so I didn’t for them, the only time I did was when I took the mic for the drive-through, and used my Good Morning America voice for clarity to the widest audience.. we all just worked together and were happy. It’s really too bad that the board rooms can’t be as accepting of differences as that Taco Bell was.