It's like this, right. Like you understand the concept of infinity. Of an everlasting expanse that goes on forever. You understand the concept, but can you really fathom infinity? Can you really understand forever? We truly can't because we live in a finite world where everything we know has borders and boundaries. We define space everywhere we go. So now you've got this idea of existence. What if I were to propose that "existence" is the natural state of the universe. That there always was "stuff". You want to think that the natural state of the universe is nothingness because that's what you can grasp based on your experiences here on Earth. If there's a couch in this room, then it's safe to assume there used to NOT be a couch in this room. How did the couch get here? Who made the couch? And on and on. But who's to say the same concepts apply to the universe? What if it just always WAS. The truth is, you understand this concept completely because these are the characteristics you attribute to your "God." He was always here. He's always existed. Why not take an unnecessary step out of the process and just say that the universe has always existed.