The reason for this has been given in the fifth verse Al-An'am 6:107 ⧉. There it has been said: If Allah Ta` ala had willed - in consideration of His own creational imperative - that the whole human race should become Muslim in faith, then, it would have become impossible for them to associate partners in the Divinity of Allah (Shirk). But, it was because of their misdeeds that Allah willed that they be punished. So, He created the necessary conditions for that end. Now, how could he make them Muslims under these circumstances? In fact, why should he worry about what they choose to do with their lives? Allah has not made him to stand guard over what they do, nor has he been authorized by Allah to bring punishment on them for their misdeeds. Therefore, he should not have any anxiety on account of what they do to themselves or for themselves.