Why?

My three year old has been in the "Why?" stage for a while now. She can take the "Why?" question all the way out to the point that you just don't know what to tell her, and "just because" isn't good enough for her. So at one point when trying to think of answer she would understand I just simply said " Because God made it that way". I've had to reach for that answer a few times now, and she accepts it with a smile. At what point in life does " Because God said so", or " God made it that way" begin to not be good enough for us? When things are difficult, trying, or just simply beyond our reasoning we find our selves asking "Why?". So WHY is it that we can't just accept "Because made it that way"? Just another advantage of innocence to think about today.