Unfreeze Change Freeze

In the early days of change management and to some extent today the mantra of change management has been focussed around Lewin’s 3 steps. Since Lewin passed before the concept of unfreeze-change-freeze could be clarified, the question remains, why does unfreeze-change-freeze not work.
Recently I participated in an organizational transformation exercise that followed a unfreeze-change-freeze approach which in the end failed.
As a result of my participation in the Systems Change Learning Circle, I have begun to understand the value of exploring the system of interest and systems of influence and their impact on organizational transformation. In moving on to my next assignment I expect to challenged on why unfreeze-change-freeze does not work and why understanding systems changes does.