One word: MONEY [Linked Image]

From the POCO end: Extra transformers, 4-wire service drops, three-phase metering, and in a lot (most?) of the residential areas, lack of three-phase primarys. (And let's not get into the whole open-delta thing, please.)

From the homebuilder's end: Increased cost for the 3-phase panel and main breakers. Increased cost to wire up the appliances.

But it would be more efficient, agreed.

Stupid should be painful.