All industry uses three phase supply, while residential service is restricted to single phase ....all the motors that drive furnace blowers, heat pumps, frig/freezer compressors, air conditioners, etc are all wasting probably 1/3 of the electricity to run them. The three phase motors also require lower amperage per leg, therefore less copper wire for major hookups, which was not an issue when copper was cheap.

The construction of three phase motors is simplier (cheaper? less copper?) ...no capacitor, no centrifugal switch start mechanism ...more reliable service
It was probably a arbitrary decision made in US just after Tesla convinced the world about AC vs DC ??

We are talking about savings of 1/3 of the major electric consumption in a residence...this is NOT insignificant...but we will have to live with it!

Slightly OT: I recently replaced a 40+ year old Sears 22cuft chest freezer with a brand new model for $400 ...it only runs at 1+amp ie 130 watts and reduced my consumption to 1/5 ...at $0.12/Kwhhr, it will cost me $36/yr vs $172 or a three year payback ...didn't realize the extreme until I got a Kill-A-Watt meter!

Now I am looking for a fractional hp DC motor to drive my squirrel cage blower in the domestic hot air system to replace the standard AC 1/3hp been running for 30+ years.
Need to determine wattage vs rpm of that unit.