It was partially to distribute airports across a few extra continents/regions for the continent based open skies model. Having only NA/SA/EU/Asia/Africa/Oceana is notably a few less then the current options.
Part of it also has been because of weak regions needing support. Mexico is typically considered part of North America (as is Greenland i might add), but Mexico is in Central America because it is both spanish speaking and represents a decent bulk of the airports present in CA. without Mexico, CA would be far FAR less viable of a region and the remainder would have to either be merged into North America or South America (into a "Latin America" continent). Neither are very appetizing to me or stephen at the moment, as we've seen some explosive growth in the number of airports offered we don't wish to be too hasty in cutting down on regions. NA is already a relatively favorable region for both quantity and quality, so why do we need to add the majority of the quality and a good chunk of the quantity airports from CA to it? Greenland between Europe/NA is kind of a null move.
Turkey was moved to Mid-East because the traditional definition of the mid-east is basically anything inbetween the borders of Iran, Turkey, and Egypt. Europe is a strong continent, so it could afford to lose Turkey giving the Mid-East a better chance of being a viable starting place for airlines. Africa is far too weak on quantity and quality of airports so it cannot afford to lose Egypt, so Egypt has remained.
In the end, it's mostly conceits for game play reasons.
