No logic. 3-phase don't cut down on your electricity bill. It is for ppl who uses a lot of electricity - i.e. high load.

For example - single phase supplies up to 20A. You have many machineries that consumes up to 30A at any given time. That will overload your powerline.

So, you install 3 phase and distribute the load. Blue phase 10A, red phase 10A and yellow phase 10A.

Another use for 3 phase is to run 440VAC appliances. I doubt you have any.