I wonder what would happen to a steer tube in a rolling machine like this one I think too that since the threaded portion of a steer tube is relatively short it doesn't make sense to roll a short amount, especially if using a mandrel is necessary with thin wall tubing. I also agree that the strength of rolled threads isn't really needed in a headset. The video also explains some of the reasons to use rolled threads and none of them really make sense for steer tubes.