The need for "a reason" is a vanity of human cognition which attempts to interpret all within the simplistic paradigm of "cause and effect". The associated need for "a creator" is merely another example of such anthropocentricity.
Maybe you have an intellectual duty to escape from your religious conditioning. THAT is as a good a reason for "existence" as anything some preacher has a vested interest in regurgitating.
There is no reason for human existence, nor for the existence of anything else. Things dont need a reason to exist, anyway.
That, then, makes us ask "Why is there something rather than nothing?", but, if you think about it, thats the same as asking why the laws of physics work the way they do. The universe simply exists, there is no reason for that nor ever will be.
And dont let yourself be fooled by the fact that the world seens to have been created for humankind. Its quite the opposite: The world was there, and humankind shaped itself to fit on it. Natural evolution and etc.