"Models can give us a helpful insight into how the change process works."
In other words, they aid managers in decision making that will cause a change in the workplace. In the case of Lewin's unfreeze/change/refreeze model, it is generally for longer term changes that look at cultivating a 'culture of change' - that is, the method and attitude of the workplace - nowadays cultures are receptive to change and generally open and communicative. The force field analysis on the other hand is useful to examine basically who is for and who is against a certain change, be it shortening a lunch break or introducing new technology.