Because there is no evidence that disproves His existence, only theory, speculation, etc. But:
The evidence of His existence is clear.
And those whom He guides have no doubts.
There has always been and always will be those who will try to disprove His existence by theorizing that all of this came about without intelligence, but it takes intelligence to mimmic life, like robots, designed after humans, cameras, designed after the eyes of humans, planes, designed after birds, etc. So there’s no evidence that there is no God, but just by trying to mimic life and failing, is the very proof that there is A God.
A human is far more complex than a robot, so how can one need intelligence to come about but not the other?