Would you like if all people became atheists?

[Silver]

I would also say that the knowledge of God's existence is also innate.

I have to disagree, because atheism is always the default position. The only two ways I know of for someone to learn of the concept of God is through indoctrination or creating the concept himself without help from any outside source. Unless one spends a solitary life in a cave without internet access, no television, and no books, the latter is not likely to happen.

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if religion does not offer any benefit to society - why have it?

The only thing that comes to mind for me is that people hold onto it for the sake of comfort much as an infant does a pacifier.