How come " why come"

Hi,
My friends an I had an argument the other day on whether it is appropriate to use "why come" in sentences where it might sound more appropriate than "how come" .

Does anyone know for sure if it is grammatically correct to do that?

I haven't heard "why come." The traditional phrase is "how come." It makes sense as a shortened form of questions like "How did it come to be that Antarctica is covered with ice?"

I have heard "why come" in the past, although I no longer hear it. I thought at the time that it was a deliberately ungrammatical piece of whimsy, an amalgamation of "why" and "how come." Does anyone know differently? SS

I believe it's chiefly used in Ebonics, or Urban slang, or Hip-Hop slang.