Some people argue that the universe has always existed. It has no causes and requires no causes.
I have no problems with it if nothing ever existed. But now that we know there is something - the universe that we are in - we have to ask: why? Why does the universe exist at all, instead of there being absolutely nothing?
Add to that the Big Bang Theory - which says there is a beginning to the universe. Now there is more reason to ask: what caused it?
To many of us, the answer is God.