I'm guessing this means you don't have any studies to back your claim. Neither do I, but in my experience most code is left to run when someone leaves the company. If issues come up, someone is assigned to support the code and nine times out of ten (okay, maybe eight) the person on support decides to rewrite the code. FWIW, the six billion people stat hardly seems relevant, right?
So you have a study? Because I’ve seen way more people who think readability in code is paramount, and I don’t think I’ve ever seen the take that it’s usually never read again.