This raises a question: Aside from tradition, why don't we use delta-only distribution with ground fault protection? All downed power lines would immediately trip the substation breaker. The same number of conductors would be required, the only additional expense would be insulators for the second phase (which is now a neutral in single-phase runs), but you'd save a conductor on three-phase runs because no neutral would be required. It would almost completely prevent injuries from downed power lines.
