Requirements volatility is the core problem of software engineering
I often hear people say that software engineering is a joke compared to civil engineering or other kinds. But they forget that when a civil engineer designs a bridge he doesn't start with: "We don't know exactly what weight it should support yet, but just start building the bridge already". And he doesn't finish with a: "Ah, turns out we wanted a tunnel instead of a bridge, can we change that next sprint?".