Why is the time repeated over and over in "There Will Come Soft Rains"?

The repetition of the time by the house is one of Bradbury's literary expressions of science and technology substituting for human thought. After the nuclear blast, this repetition becomes meaningless, demonstrating the absurdity of this substitution of technology for humanity.

In the narrative of Bradbury's story, when the time is announced, various objects appear in order to enable the residents of the house to conduct their routine activities. For instance, at "Two thirty-five," as it is written in the narrative, the bridge tables emerge from the patio walls. Playing cards and all that is needed for the card game are set out by automation. Then, at four o'clock, the tables fold themselves and are automatically taken back through the walls' panels. Next, the house announces "Four-thirty" and the activity for this appointed time commences. Thus, the time is announced throughout the day with its mindless regimentation of the inhabitants' lives. Absurdly, the house continues its routine even when the residents are no longer there.

The house was an altar with ten thousand attendants, big, small, servicing, attending, in choirs. But the gods had gone away, and the ritual of the religion continued senselessly, uselessly.

For all its convenience and capabilities, technology cannot substitute for real human thought and creativity. Because the house has continued to senselessly fill bathtubs and sinks with water according to its programming, the reserve supply is depleted; consequently, when a fire starts on the stove, the house's scurrying water rats and wall sprays cannot extinguish this blaze and the house is destroyed. 

Throughout many of his literary works, Ray Bradbury expresses his fears that technology may surpass its value and in its power become a detriment and even a destructive force to humanity. "There Will Come Soft Rains" is a story that demonstrates humankind's growing dependency upon a dehumanizing technology as well as a lack of control over some of our scientific developments. Certainly, the nuclear blast that kills the family exemplifies technology out of control.