Do they make 10-2, 8-2, and 6-2 NM cable with black and red conductors, rather than black and white? This would actually make a lot more sense if they did, since there are no 120V loads above 20A, thus they wouldn't need a neutral wire. In fact, I don't know why they even make 30A single-pole breakers. With that being said, are we still required to re-identify the white wire as a hot when using 10-2 and larger NM cables? I always do with 14-2 and 12-2, but never with 10 or larger.