what you forget is most “major drift cars” are pretty big hp cars as well, so like stephon said, the less camber/more contact the better as far as traction is concerned, especially with that much power to the ground. On lower hp cars, it makes breaking traction that much easier.
It mostly is a style thing, that and a fitment thing. To have a flush wheel on a low car stretching the tire helps it fit in the wheel well better.