Because I don't really care. I don't need to have what you will accept as a cogent argument to feel comfortable, or to earn your permission to not believe. I don't believe in any gods because
1) it's clear to me they are made up by humans (mostly because of all the human attributes they supposedly have, like jealousy and anger) and
2) the existence of the universe doesn't need explaining. It's here because it's here. To me, that's the end of it. I attempt to answer your questions because you asked them, not because it matters.
“Because I don’t really care.”
Well, that’s a relief. If you don’t care that your own arguments are flawed, then I don’t have to waste anymore of my time pointing it out.