One benefit of this is that the Holy Quran possesses within itself every necessary teaching. Its tenets are more than sufficient to uproot every false doctrine or ill teaching that could possibly exist in the world. This is the deep wisdom and power of Allah the Exalted.
Since this perfect book was destined to bring about perfect reformation, it was necessary for spiritual disease to be at its peak at the time and place of its revelation as well. This was so that a perfect remedy could be provided for each and every malady. As such, this peninsula was home to ailing people of all sorts, who suffered from every spiritual illness that was to afflict the people of that age or those of future generations.
This is why the Quran brought all religious law to its perfection. At the time of the revelation of other books, neither was this needed, nor did they possess such a perfect teaching.
(Hazrat Mirza Ghulam Ahmadas, Malfuzat, Vol. 1, pp. 37-38)