At the point at which the population exchange was agreed, most Greeks from Asia Minor were already expelled. Many of those were settled in areas with a significant Muslim population, so without an population exchange there would be a potential conflict between the local Muslims and the Greek refugees. This would probably lead to further flight of Muslims to Turkey and in turn to more Greek refugees to Greece. In the end, there would be an effective population exchange, only far more violent, which is what the orderly population exchange aimed to avoid.