In the case of Tiger Woods, it plays a part because black people used to be banned from golf courses.
I don't know if black people were ever banned from tennis clubs; I bet at times there have been big barriers to them joining, if not an official ban.
These are sports where a bit of money traditionally used to be needed to start up, unlike rugby or football, say. And traditionally, in the US and Europe, black people generally had a lot less.
So skin colour has loads to do with it. I bet it was a lot harder for Williams and Woods when they were young than their white peers - perhaps that's where the drive to win comes from.