In "There Will Come Soft Rains," so many things are happening at once because the house is programmed to execute multiple functions at specific times in the day.
The house is a marvel of modern technology. We see this when the house blares out its responsibilities at precise moments. At seven in the morning, it wakes people up, while at 8:01, it tells the children to hurry off to school. At 9:15, the house begins cleaning, while at five in the evening, a bath is drawn. The house knows that, at these moments, certain events must simultaneously take place. For example, as the house reminds that it is time to wake up, it gives them reminders for the day: "Today is Mr. Featherstone's birthday. Today is the anniversary of Tilita's marriage. Insurance is payable, as are the water, gas, and light bills."
The house has been programmed to assist human beings with multiple tasks at specific times. It simulates daily life. This is why there is so much happening at once in the house. In day to day life, we are never doing just one thing. There are always other events that happen at the same time. For example, when we wake up in the morning, we think about what we have to do for that day. When we get the kids ready, we are also making lunches and ensuring that everyone is dressed for the weather conditions outside. We remember that certain bills have to be paid and other responsibilities must be met. The house mirrors this tendency. The house replicates human activity even though no humans are living in it.