To formulate theorems based on this model often encourages enormous ingenuity and mathematical skills. The fourth reason is that some see it as providing an ideal standard by which we can judge how far we fall short of the ideal. It is something to constantly aim for. In fact, once the model's unreality is accepted then it cannot be something to ever aim for. If we see this model's emphasis on perfect competition only as an abstract construct which at best implies the value not of perfect but of vigorous competition then we must evaluate its virtues in the light of a host of other considerations.
Vigorous competition is never an unmixed blessing and therefore the market is never one either.
Even the functioning of the market can never be separated from the historically shaped character of any given society. The latter is also theoretically divorced from wider and deeper considerations of sociology, politics, history, culture and international relations. As long as this remains the case the trajectories and characters of actual economies will remain essentially impervious to the understandings of conventional economists.