Because there are no wires or anything to indicate electricity is actually at work. Instead, suitcases scoot along the floor to rooms where clothes put themselves away. The couple that checked into the hotel enter their room, clap their hands, and a table comes scooting into the room with various buttons on it. They push buttons and have their hair combed and rearranged, the man has his beard shaved, and their shoes are polished while they are wearing them. They push another button and letters are written letting their loved ones know they have arrived at their destination safely. For you Gen Z kids, letters are what we wrote before texting was a thing.
As the couple retires for the night, there is a message in the film about the dangers of relying too much on automation. A drunken night watchman throws the switches on the electric system in such a way that the entire thing goes haywire and the furniture is jumbled about, tossing the guests around in the process.
This film used stop motion to obtain the effects seen, and is one of the earliest uses of that method to tell a story. It's also an example of a rare surviving early film from Spain.