Have you ever played, say, Mass Effect with a black character? Or Dragon Age 2? I'm not even american and i wouldn't do either, simply because i've heard enough people talk to know the voices don't fit. It's the same general concept. Voice is a part of roleplay since forever, and it can detract from the experience more easily than it enhances it if your character doesn't fit their voice. For example, in Fallout 4 i couldn't play anything other than a depressed dad going out for milk, unless i got myself the silent mod (urrah) or tuned him out constantly.
Not sure what black people you have hung out with, but they don't all talk ghetto. I know a number of people of color that on the phone, you would have no idea what race they were.
not to derail this, but using the phrase "talk ghetto" would be considered inappropriate (some would say racist). AAVE is the more linguistic term for it (African American Vernacular English). It's actually quite an interesting subject (that I know almost nothing about lol)
