As Muslims we believe in the infinite wisdom of Almighty God and we do not really know the absolute real reasons as to why certain things occurred in certain ways throughout the history of mankind.
According to one strong view, there are only the names of 25 Prophets mentioned in the Quran. And so this leaves another 123, 975 Prophets, in which some have been mentioned in Hadith, and many have not been discussed (See: Surah al-Nisaa`, verse 124).
Please ponder on these points:
The first principle is there is no group of people without God having sent to them a "warner" (Surah Fatir, verse 24/ Surah al-Nahl, verse 36).
Another problem is many Prophets were sent, but their people rejected them, calling them magicians or insane. (Surah al-Dhariyat, verse 52). If throughout the Prophet that was sent to them was rejected or killed, then the next generations will not have any information about him.
Why is it that in the history of mankind we only have written material reaching us from certain areas in the world. Not to say that other parts of the world did not have civilisations, but they do not have a written heritage in this particular meaning.
Based on narrations we cannot say that Prophets were only limited to the Middle East, but as to why the Quran speaks about this particular area of the world, one reason we can present is that it needed to have been relevant to the message of the Prophet (s.a.w.) and information on personalities that people of that time can relate to.
Furthermore, many Prophets came from the lineage of Prophet Ibrahim (a.s.), so naturally they would be in this particular region.
And Allah knows best.