Range safety during a typical *controlled* ballistic missile interception costs north of several million dollars. Firing live missiles is always fraught with danger. Sort of like starting a shoot out in Times Square. But they drew first.
Yes we have the capability to shoot down those tests, but we also have the ability to assess in seconds the trajectory whereby we can determine where it’s going.
So knowing it’s a test why would we reveal tech we otherwise don’t need to.
By using it and other associated tech we would be revealing capabilities to China and Russia we might otherwise not need to.