Why does Allah ask questions though He knows the answers?

My question is as follows: There are two verses that many atheists share in social media.
The first one is verse 99 of the chapter of Yunus: “If it had been thy Lord's will, they would all have believed.” The second one is the question in verse 20 of the chapter of al-Inshiqaq: “What then is the matter with them, that they believe not?”
Atheists answer it as follows: Because You did not will.
Why does Allah Almighty ask that question though He knows the answer? How true is the answer that atheists give?

Dear Brother / Sister,

The meaning of the verse in the chapter of Yunus is as follows:

“If it had been thy Lord's will, they would all have believed,- all who are on earth! Wilt thou then compel mankind, against their will, to believe?” (Yunus, 10/99)

The verse above consoles the Prophet (pbuh). The Prophet (pbuh) wanted the people to believe very much. He felt sad when they did not believe. That fact is expressed in several verses in the Quran.

The will mentioned in the verse is related to creation.

Allah has two kinds of wills.

One of them is the will related to the decrees of divine revelation. That will expresses Allah’s consent and gladness but it is not compelling. For example, although Allah wills, many people do not believe. Similarly, there are many believers who do not fulfill their religious duties such as performing prayers.

It is aimed at giving opportunity to man’s free will for the realization of a fair test. That fact is underlined in the following verse: “Let there be no compulsion in religion”.

The other is the will related to creation. The second will is compelling. If Allah wants to create something, nobody and nothing can prevent it. That will related to creation is pointed out in the verse in question.   

The sentence in verse 20 of the chapter of al-Inshiqaq is not a question in the sense that we understand. It is an expression of astonishment in the form of a question:  

“What then is the matter with them, that they believe not? (Ma lahum lu yuminun?”) 

That is, what evidence do they have for not believing in life in the hereafter though we show them so many verses and scientific evidences?

The question in the verse is not a real question that expects an answer or that wants to find out something. It is an expression of astonishment. (see Razi, Qurtubi, Ibn Ashur, Maraghi, the interpretation of the verse in question)

Suppose that a father asked his child who was a student, “Did you get these marks? Do these marks really belong to you?” when he saw his school report. It does not mean that the father does not know whether they belong to his child or not; neither does it mean that he wants to learn something with that question.

Questions on Islam