Because of temptation factor, and resistance. If we can't resist the temptation then we fail, but if we resist the temptation, we are absolute winners.-> To religious people especially Muslims since there is a few religious Christians here : If god existed why did he create us ? If your answer was to test us then did Allah say that he knows everything ? Like he knows what would happen in the future etc. ?
If we religious people can't prove God existence visually or physically.
Then I'm gonna prove Satan does exists which will lead to the existence of God.
I'm gonna work on it.