Because electricity just comes out of those little outlets in the walls....
Way back when they had a Exhibit at Disneyland sponsored by GE called the Carousel of Progress. It showed the advances in modern living throughout the years.
On the way out you passed a miniature all Electric City surrounding a Nuclear Power Plant.
Before that they had the all Electric Monsanto House of the future.
https://en.wikipedia.org/wiki/Monsanto_House_of_the_Future