In discussions on Agile, change is often limited to responsiveness to new (late) requirements.
But most of the change I experience, is our *change in understanding*. While we explore and build, we understand more of what we are doing (e.g. the technology we use) and more on what is valueable (e.g. does this feature helps you?)
The initial uncertainties does not just evaporate when time passes. We reduce the uncertainty by building something working based on our best assumptions, prove whether this flies, experiment, observe and adapt. This is active learning process.