Why don't people prevent earthquakes? Why do we have to wait for death?

Because earthquakes happen every day, humans can know in advance, but they can't accurately measure where the epicenter is, and they don't know how big the magnitude is and how much damage it is. So, they can't just broadcast it. It's too late to know it's a big earthquake. If you want to be accurate and reliable, people like you will come up with some practical methods.